In my observation (for what it's worth which might be nothing!) we seem to have gone through this kind of "evolution" of movements in parenting - and this is how I see it. Feel free to correct/argue/disagree! I'm guessing at the timescales.
First (80s/90s?) there was a shift from physical/mental domination of children in order to frighten them into behaving to the idea of token/mildly annoying punishments which still give the message that you've done something wrong, or are bad enough to want to avoid, but don't actually traumatise the child - e.g. naughty step/spot/chair, sending to room, missing playtime (in schools), stopping pocket money, removal of a favourite toy, grounding, etc. Later as screens start to play a massive part in a lot of kids' lives you can add screen ban to this list. I think of this as "Supernanny" type parenting. It's simply replacing older physically dominating methods with nonviolent methods, but nothing else about the parenting is changed really. You're just swapping the threat of a smack/beating for the threat of grounding or naughty chair. However because the penalty for misbehaviour isn't scary any more, what becomes really important is consistency, clear expectations and routine - many parents struggle with those things. And for many children who might struggle with certain expectations, although they are not being constantly hit/living in constant fear any more the lesser punishments may not work for them at all, which is where you get the idea that "parents are too soft these days".
Next or as a response to this (late 90s/2000s), there was more of a shift towards "Positive parenting" or the idea that too much punishment/telling off can still be harmful to a child's self esteem, even if they aren't awful or terrifying, and create a self-fulfilling prophecy where a child is always told they are bad/lazy/mean and so they will act bad/lazy/mean. So instead you look for reasons to tell them they are good/hardworking/kind and they will become that value. Reward charts became popular, parents were urged to "praise the good, ignore the bad" and "label the behaviour, not the child". Naughty step was out, thinking step/time out was in. There's a lot of good, sensible stuff here. You get more out of people in general by encouraging what you want rather than just yelling at them when they get it wrong. But I think a lot of people took the idea of negativity being damaging to heart and took from this that it's important never to let children have a negative experience because it might damage them. And I don't say that in a judgemental way, because I can absolutely understand where that mindset would come from. But anyway, this approach is too simplistic because it still does not offer a solution to unwanted behaviour which persists despite punishment and/or positivity.
So the next response (I want to say late 2000s, although it was present before, even currently used schools of this have been around since the 60s/70s, and anybody who has worked with "difficult" children in ANY time period knows this from experience - but this is when it became popular enough to be mainstream, IMO) and very familiar to me because this is when I had DS1, is the idea that all behaviour is communication, when children misbehave, it is because they have an unmet need. This tends to be the "gentle parenting" school of thought, e.g. Taking Children Seriously/Unconditional Parenting, often highly correlated with attachment parenting, and a lot of the focus is that you don't punish bad behaviour, because the behaviour is either a misguided attempt where the child does not know any better yet (and it's better/more effective to teach them the correct way through kindness/modelling/reason than threats, or just wait until they are older) or it's an expression of some kind of trauma or unmet need, which you can work through and that will stop the behaviour. It's also a shift in mindset from the idea that parents automatically know best and should control their children's behaviour through the use of reward, praise and/or punishment and reasoning. Instead the idea is that children are learning, they don't always get it right but we should support them, and also, that it's important to listen to children and take on board their point of view. Sometimes the adult will know better because of their life experience, but not always. So there is also an encouragement to pick your battles somewhat and not go after every little thing.
Most recently, I am seeing two more approaches/responses pop up at the same time. One is about persistent behaviours being related to lagging skills and so methods to explicitly teach those skills (which I think is fantastic actually, but has very little to do with this discussion). The other is a concern about the way "gentle parenting" resources often discuss boundaries, and a common pattern which is that people who tend to be conflict avoidant and/or struggle with personal boundaries and/or have people-pleasing tendencies tend to be drawn to a parenting style which promises that you will never have to punish your child and you don't need to engage in power struggles in the first place. There's a very good explanation/examples of this here.
That's the missing piece of the puzzle IMO and the part that has been lost. I don't think it's overly helpful to blame parents - parents only ever do what they can and what they think is best for their children. I honestly don't think that a lack of boundaries or an avoidance of anything negative has come from a place of laziness - it's misguided but it comes from a good intention. We probably had to move away from the overly harsh methods of boundary setting in the past in order to create and understand the importance of boundary setting as a fundamental thing.
Sorry I'm getting a bit rambly, because I'm tired and I'm going to go for a sleep but I really wanted to get these thoughts down because I've been wanting to for a while and I think it's quite relevant here. I'll be back later (possibly) or tomorrow if I don't get up again! I will try and read one of the articles, as I've only skim read this thread's response.