What's replaced it? "Naughty step" was more a less a version of "time out", has something else replaced time out?
I think what's changed is less the exact punishment that is used, and more the role that punishment plays in up to date (evidence based) parenting advice.
It used to be assumed that if you see your child doing something you don't want, you should reprimand them, and quite likely punish them as well, (or at the very least warn/remind them of the threat of punishment if they continue) so that they associate that action with something unpleasant, and hopefully discourage them from doing it. Certainly that was the role that smacking played, and I think the "Supernanny era" time out/naughty step played that role too, as you can see in this description from the supernanny wiki (no idea if this is official guidance or fan-written taken from tips on the programme):
https://supernanny.fandom.com/wiki/Timeout
Some quotes:
Do not have the time-out zone be in either the child(ren)'s bedroom or a fun place, otherwise the child would either get mixed messages or play with their toys.
Make sure that the time-out area doesn't have anywhere comfortable to sit on. (WTF)
4-year-olds stay for 4 minutes, 7-year-olds stay for 7 minutes, and ages are sometimes rounded up
Do not pick the child(ren) up, [after the time out when offering a hug and kiss] otherwise they will think you are apologizing for being cruel. (!!!!!)
Should the child(ren) refuse to apologize, they shall remain again in timeout for the same additional minutes depending on their age until they choose to apologize after the expiration of their time.
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That's clearly a punitive definition of time out; it's not supposed to be fun, it's supposed to be a deterrent, if the child experiences it as "cruel" you should not apologise for this. The WHOLE point of it is something that the child wants to avoid.
My perception is that this is outdated, because more up to date parenting advice does not see bad behaviour as something which just exists all by itself and can be squashed independently of other things. You are supposed to view the behaviour in context.
Either (especially in the case of a pattern of generally poor behaviour, rather than a specific incident) it's an expression of unmet needs, ie you want to look at the whole situation more generally - does this child get enough sleep, is their diet OK, are they getting enough fresh air and exercise, do the parents behave warmly towards the child, is the child stressed/worried, are they attention seeking because they have a new sibling etc etc. And yes, undiagnosed neurodiversity is relevant here. And so with that you would want to look at the wider picture and address the child's needs, which should reduce behaviour, rather than simply punishing them in the hope the behaviour will go away without addressing any of the underlying causes.
Or it can be seen as more of a two sided thing; the idea that for every negative behaviour, there is a positive opposite. The assumption may be that if you discourage the bad behaviour, then the good opposite behaviour will automatically grow, or it might have simply been that neither are connected. But actually, what research tells us is that it is generally more effective to identify the positive opposite behaviour and encourage that, because if you've got this right then you will see the bad behaviour automatically shrink/stop. So praising/rewarding politeness is more effective more quickly and with a more lasting effect than punishing a rude tone, for example. And clear communication of what you actually want/expect your children to do is really imperative, and sometimes they need some help or encouragement to develop the wanted behaviour because they aren't very good at it yet (example, a child who frequently gets frustrated and lamps their sibling may need some training/practice/guidance in calming down techniques, which punishment will not teach). This is not particularly new information, we've known for a really really long time that positive encouragement works better than negative deterrent. But I think it's taken a while to really filter into common parenting attitudes, and I think this is really where we are right now in the majority of Western/English speaking countries' parenting advice.
And so I think that while most people still do use punishment in some form, it's recognised that it's not the most effective tool in a parent's toolbox, others are better. We also know that the severity of the punishment doesn't make very much of a difference in how well it deters behaviour, so there is no need to make a time out very boring and long for the child - a minute or so, mainly with the purpose of taking the child away from the situation and creating some space for them to calm down, is sufficient. Occasionally you might want a deterrent which is where something like removal of privilege would come in, but even this is something that you would want to use sparingly, and be looking at the overall picture to see if anything is lacking or looking at the specific behaviour and thiking about what would help in terms of supporting/encouraging the opposite.