Ultimately, Lemmy is a Reddit clone and one problem with Reddit-like platforms is the upvote/downvote system heavily promotes groupthink since dissenting opinions are downvoted into oblivion while consensus opinions are promoted. Lemmy attempts to solve this problem by being open source, self-hostable, and federated (which are all great things), but these aspects alone can't totally solve the inherent groupthink problem, it just makes it easier for those with differing views to spin off and start their own instances, which will likely have their own groupthink.
As politically centrist myself, I've basically just unsubscribed from the political communities and focus on the more tech-related ones. If an apolitical or more centrist political Lemmy instance which federated with lemmy.ml was started there's a good chance I'd join.
I think YouTube Vanced is no longer supported by the devs and it was never a privacy-focused project anyway. There are plenty of FOSS Android apps that can stream YouTube more privately though. NewPipe is probably the most popular.