I would say largest problem with leftist spaces is a little more challenging to identify; it's that leftists are broadly intellectuals or at least identify as intellectual because of effort they put into honoring nuance. And the primary opponent of leftists are conservatives, and they are proudly not intellectual and view people who use the lens of intellectualism and nuance as weak or elitist.
Because it's incredibly difficult to have any kind of meaningful intellectual debate with your opponents, we have all retreated to our safe-spaces and online bubbles, our discord groups and algorithm-driven feeds. We don't even walk in the same environments or view the same media anymore,
So in order for people on the left to feel any kind of satisfaction and feel like their mental strength actually has a use, they find someone else who is ostensibly on the left and attack something that person said or did which they feel does not represent their own leftist values.
Our eternal, infernal infighting problem is because we have an army of head-warriors who have no heads to butt against. Even if there were people on the right willing to have intellectual debates, they're not even in the same talking-space anymore. The only place you can go to have debates are contentious battleground where nobody is even arguing in good faith and just screaming their talking points for audience upvotes. So leftists, being humans, take the easy path and turn on each other to feel like they're making any progress or are involved at all in making things better.
On the right it's much easier to feel like you're part of the movement or doing something for your group, all you have to do is buy a gun or stockpile trumpcoins and canned food or harass someone or get drunk and scream about minorities. It's mindless and pointless but it feels like action. And sadly, more and more people are being turned away by this kind of mental effort and emotional labor of "doing the right thing" so they're getting sucked in by the mindless orcs who have more fun and have easier victory conditions.