I consider myself a more moderate, laid back person and I've browsed A&N for a while. I think that the main problem is that a lot of the people screaming at each other are the same kind of person on some level. When people don't have a lot of life experience or perspective, there's a general psychological cycle that you see when forming an opinion on the hot topic of the day. Someone researches their side, investing time and energy in forming an opinion. They then hold up this small level of expertise as a facet of their self-worth - 'I'm and intelligent person who came to this good and reasoned perspective'. They do this over and over again, and eventually get a very inflated sense of their own reasonableness and/or virtue. They become attached to these little facets and incredibly militaristic in defending them. Psychologically, the idea of someone else being reasonable and reaching the opposite conclusion is seen as a threat to their own fragile self-perception.
The classic example of this is the youtube atheist vs. evangelical slapfights of the oughts - some people based their sense of enlightenment on a bunch of religious people being troglodytes, and others based their sense of virtue on their religious affiliation making them superior, and they saw one another as entirely evil or virtuous with no gray area. You see this here in the Ukraine thread - there are a lot of absolute spergs on both side who parse very hazy, fog-of-war information and incredibly complex geopolitical issues through this same defective prism - anyone who disagrees with me is a vatnik/russaboo, or everyone who disagrees with me is a reddit soyface hohol. In China threads, you've got libertarian partisans who are constantly acting like you're a retard if you don't think that Shanghai is going to sink into the East China Sea as the Three Gorges Dam dissolves into a fine dust any day now. I've read the vaccine/covid thread, and I've seen the same people who complain about A&N being a shithole just adding more shit to the pile and acting in this same blinkered, partisan manner, often while many A&N denizens attempt to engage them in a much more mature and sensible way. The crucial problem is the one I outlined before - these people think that the views of the A&N users on covid or vaccines make them retarded, paranoid, or evil, and so even when the A&N poster is respectful, reasonable, and constructive they are dismissed and shit on in a way that isn't constructive, or even a good-natured jab.
Why don't the A&N users assimilate? Well they really can't if they're shoved into a containment board and given the kiddie version of ratings to play with. To digest a pool of new users you need to cut the influx (that's already been done) and then actively work to integrate them into the site. And once you've digested what you can, you shit out what you can't - the users who are just giant spergs who can't play nice have to be banned or contained. Not for saying nigger or talking about Jews , but just for being so socially retarded that they cannot function on the site. If existing users yell that the new posters are too inflexible and spastic, then they have to be held to that same standard, and that's a cultural problem that needs to be sorted out among established users. It just becomes difficult because people build social capital on any site, and people are human and are more forgiving when they know people, and less likely to be charitable to newcomers. But as long as this isn't done A&N will fester in that twilight zone between a containment board and an integrated subculture.