IMO (and I can't ever if I've already alluded to it on here - I don't think so) part of the problem was Gove's 2014 curriculum revamp.
We do PSHE lessons every week. My class know all about empathy, self esteem, self worth, what a good friend looks like, how to resolve conflict harmoniously... theoretically. I can ask any of them, and they can all give me the right answers. But they have no practical application.
Pre 2014, if children fell out at school or there was a problem, the TA would take those children put in the afternoon for 20 mins and work with them. They'd do self esteem building activities, they'd do conflict resolution activities, they'd run friendship groups.
There is far less of it now.
TAs (if you're still lucky enough to have one!) are.running handwriting groups, times tables groups, pre teaching sessions, booster groups, interventions... and the social and emotional aspects of learning are abandoned.
We see the sort of S and E issues in UKS2 that would have been dealt with in KS1 and LKS2 but now the kids are bigger and with a healthy dose of hormones chucked in for good measure and they're far less compliant.
The curriculum is so crammed, and the focus so much on 'coverage' now that we are grabbing every spare few minutes to squeeze extra learning in. We don't have time for circle times, or kindness activities (where you say something kind about the person siting next to you). We don't have time to sit and chat with the children the way we used to.
I sometimes do extra playground duties just so I can chat with them.
Where children come from kind families, its less of an issue (I had a boy come up to me last week and recommend one of the girls in class for the end of week certificate because she'd helped him in numeracy that week) but where they are not raised in kindness and empathy, they are often in survival mode and they just don't see others. They have no empathy.