I don't know. I watched her interview on We Need To Talk and I have to say it completely changed my impression of her. I realise that she could have been spinning for positive PR but I hadn't realised that she had veto power in choosing which families she worked with, and she said no to certain things the production team wanted to do because she didn't feel it was in the best interest of the children. Or the amount of hours that she spent with each family. The programme made it seem like she breezed in and out and was barely there for any time at all. She also seemed like she really wanted to help people even though I think her advice is sometimes a bit too narrow and one-size-fits-all.
I started watching some of the older/original episodes again and it made me see them from a different angle. The editing and voiceover is very much focused on "Look at these TERRIBLE, NAUGHTY children and Supernanny is here to SORT THEM OUT!!!!" but she doesn't actually do or say much to the children directly. She does it a couple of times to demonstrate to the parents what to do, but what she is actually doing is parent training. And while the approach is really dated - I cringed at the first episode I watched where she grabbed a child by the wrist and dragged them by the arm to a corner to face the wall and be told "You face the wall because you have been BAD." - It is 22 years old. I haven't watched the more recent USA episodes, so I don't know if those ones have more updated wording, although USA seems around the same stage as the UK was 22 years ago in terms of how hitting/smacking is generally seen. It strikes me that it's not especially safe handling, yanking children around by their arms is not something that would be allowed in a school for example.
OTOH, I think the principles of clearly and calmly communicating to the child what behaviour you don't like, and why, and providing a calm, predictable and unscary consequence, are good and usually a huge improvement over what the parents have previously been doing, which is normally ignoring the children until they get overwhelmed at which point they shout and argue with them. What I'm less keen on with the punishment part is that it's often shown as being prolonged ie the time out continues until the child submits or apologises even if it takes over an hour. And she often tends to double up on the punishment so e.g. will use time out AND toy confiscation and by the end of the ordeal I don't think the child even remembers what they were originally being punished for. I am not sure this is strictly within the guidance of how to use that kind of thing effectively, and to me that highlights that she doesn't have the relevant training/understanding, this is something she's come to from instinct and experience, which is why she's including some unnecessary aspects such as shame, persisting until you "win" to establish dominance, and making the punishment something the child explicitly does not like, which are aspects of discipline that feel intuitive (they fit nicely into the "order and good triumph over evil and chaos" narrative) but aren't necessarily supported by research. It's all the other stuff which makes it work, this is just flair, and as long as it's balanced out overall by positive interaction, it's unlikely to be harmful but for some children, either because they have underlying difficulties which make it hard for them to meet behaviour expectations or because their parents struggle to provide the positive side, it won't be balanced and that can cause a problem.
She also mentioned explicitly in the interview that time out isn't going to teach your child to e.g. have better table manners. Practice, actively teaching and praise for that behaviour is, as well as general routine/structure and connection so you can share your family values. This doesn't come across at all in the programme, at least the earlier seasons - the programme presents it that the being yanked constantly back to the step/naughty spot/etc and told they are naughty is what changes children's behaviour, and while the "practise and praise" part is shown in each episode and she seems to tackle at least 1-2 issues this way, and the routine and/or connection is usually mentioned as well, it's given barely any airtime and the routine is always presented as a militaristic thing, so the overall impression is that Supernanny's approach is all about whipping these unruly kids into shape using military-style discipline - probably because the most "entertaining" part of the programme is people wanting to gawp at how bad the children's behaviour (or alternatively, how bad the parenting) was "before" and then that conflict scene of the unruliest child being "defeated" is included consistently in EVERY episode - it provides a chaos vs order/good vs evil sort of narrative, and that is the entertainment value, both in enjoying the conflict but also in judgement over the "before" scenario (parents and/or kids). If you read the comments on all the youtube videos it's almost all people talking about these parts of the programme.
Morally in terms of the children being exploited for entertainment, especially entertainment based on the audience judging them as bad, I do think this is hugely questionable and I'm unsure whether that would still happen today but maybe I'm naive there. Also some of the families probably needed more support - some of the children present as though they may have issues such as ADHD for example, and while clearer discipline and structure help, they won't actually treat said issues. Some of the parents also probably needed psychological input but that is fairly standard for reality TV, TBF.
The format if you take it purely as an observational/documentary/educational style thing is quite good (for the viewer) in that it shows an example of the kind of issues a parent might have (so you can see whether it's relateable) and the approach is pretty much the same each time so once you've seen a few episodes, you start to spot yourself where the parents are going "wrong" (according to Supernanny). The fact she leaves them to it for a week and then comes back also sets them up to fail, which I think is purposeful in terms of it allows you to see common mistakes people make when trying to follow the techniques, but that is my other criticism of the system - it only really works if you're using all the parts of it. If you're just taking certain parts (especially the strict telling off and shame parts and the taking things away) but not others, like the clear communication, adult remaining calm, and the positive aspects of practicing and praising and structure, then it's not likely to work and might even make things worse. Again clear trade off between what's good for the viewer vs what's exploitative for the family. And it's also all very one size fits all - Jo Frost clearly has set ideas about what is right in terms of how routine or hierarchy or family life should look, which might not fit all families in reality.
The other "retro" programme I've been watching recently from a similar era is How Clean is Your House, which I compared with Stacey's Sort Your Life Out.
HCIYH has a similar format to Supernanny - very strict, buttoned up, almost dominatrixy characters of Kim/Aggie and the first part of the programme looms in on the worst bits of the house and bits of interview with the family edited to make them look as lazy/stupid/unashamed as possible and K/A being totally shocked at how awfully dirty it is, then they give the family a dressing down about it and make them grovel and promise to do better, and THEN they sort it all out and give them a clean slate to work with, and this is presented as a kindness so you leave the programme with a feel-good impression rather than the impression of having judged the people. But again the entire entertainment value in the programme is about this defeat of order over chaos, gawping at how bad other people are, and whipping unruly people into shape using shame. Very one size fits all, too, so e.g. if someone says they won't use a particular storage system they are just told off and told that they must do it that way and it's lazy not to.
SYLO which is a modern programme is much softer and less judgemental. The team go into the house without the family and while they do have an element of being shocked by the amount of items, the focus isn't about how awful the family is, it's more sympathetic "How do they eat at this table? The children have no space to play. I wonder how it's got like this?" And then rather than having a section of shaming the family, they have scenes where they box everything up and during this time they discuss with the family what they would like to be able to do with their space and sometimes a bit of how it's got that way, and it's presented as a more sympathetic section. There is a little bit of the "order vs chaos" and "whipping into shape" in the warehouse section where they have to wrestle with how to reduce the number of items, but it's usually much softer, more collaborative, more constructive and sometimes there are moments of emotional vulnerability. Then by the end they have usually transformed the house with attention paid to the family's unique needs/wants and rather than being told no, the way you were doing it before is wrong and this is better, they try to incorporate things in and it at least comes across as being tailored to the family themselves without judgement, e.g. they might use a storage system which is realistic, like hidden baskets, rather than saying well I know you want to just be able to throw things in but actually you must line it all up neatly.