First off, political "extremism" is a very flexible term. For some, it's extremism to support a system that leaves people dying of hunger and treatable diseases while a tiny class becomes rich beyond belief and at the same time funding wars and bombings all over the globe for profits. For others, extremism is wanting to materially overturn the former, and not just on words or the imaginary marketplace of ideas.

You can block the political communities if that's not your thing, but creating a nice capitalist neoliberal bubble that never challenges any world perceptions is not the goal of most instances here, unlike Reddit.

The sign up process is a small extra difficulty, but it's also part of the reason why you're not interacting with bot farms instead of people like you do on any big platform.