This is Ba Sing Se levels of delusion for some people.
In fact, there are plenty of commentators downthread who don't see it as a mistake either. Years of demonisation and propaganda has gone into supporting the belief that as soon as somebody steps out of line it's necessary to beat them back into line, or shoot them if they do not comply. It's no more a mistake than the millions of people in US prisons: it's policy.
US police forces seem to have a very short training which, as far as I understand is not centrally vetted by any federal organism? And considering the short training time it seems to be mostly focused on tactical and firearm training.
Compare that with European forces and you see a completely different reality. In Europe the police is generally seen as peace-keepers, force is absolutely a last resort (probably not so true for crowd control units but certainly true for daily policing).
Normal summer weekend you have at least couple dozen people shot(not by cops, so you never hear about them)
Nevertheless, a large percentage of situations can be de-escalated by police forces. What is even less acceptable, is that in many cases the escalation is originating from police officers. Which is why, to me, de-escalation and conflict management training is lacking among these officers.
Going back to your point, it is a really complex issue and I am not going to claim a deep understanding of US society.
There is a huge percentage of GDP spent on welfare in most EU countries, the welfare and safety nets put in place are (mostly) accepted in the EU because of a sense of solidarity and dignity and a mutual understanding that _anyone_ can be caught in a situation where they are facing social/family/health/finacial issues. Being misfortunate should not be punished with falling through the cracks of society. I get the impression that in the US this type of belief would be an outlier.
However, putting aside the humanitarian values, there is a very practical and utilitarian aspect to EU welfare and social benefits programs, they actually detract people from marginal behaviour because it stops them from being pushed into a corner.
There is a lot of evidence that social welfare safety nets reduce crime. Equally, there is evidence that insufficient welfare correlates with crime rise. [0]
And this I think, is a huge cultural shift. The outrage in the US would be huge if we tried to rationalize that we have to take tax money from everyone, to give free-money to people on the fringes of society, in order to reduce gun violence. However, all the EU policies for the past 40 years confirm this reasoning.
[0] Social determinants of health in relation to firearm-related homicides in the United States: A nationwide multilevel cross-sectional study, D. Kim, 2019 https://journals.plos.org/plosmedicine/article?id=10.1371/jo...
Hiring and firing by this metric is also lacking.