I'd say almost every sub is, especially big ones. Especially the default ones. I've even been preemptively banned from some subs for even being in other subs. Some subs admittedly are pretty good about prohibiting politics, but that's the exception rather than the norm.
Local subs are extremely political. I quit bothering as every post is about something the governor did that literally doesn't affect the city or anyone in it.
You had everything from (hardcore fetish) porn to hobby subreddits shutdown over the admins not banning "right wing covid disinformation" subs. I agree that not all subreddits involve politics (some even have rules against political posts) but the problem is that it's so widespread that even your niche craft subreddit can have a mod that thinks anyone cares about his opinion/online slacktivism.
The problem isn't their message or political stance, it's more than they usually bring absolutely nothing to the table and absolutely no one asked for political theory classes from the internet equivalent of an unpaid internet janitor/average random subreddit user.
It used to be mostly confined to the default subs but i guess reddit grew so much (and with most of the new users using the default subs first) that the end result was inevitable
Local subs are extremely political. I quit bothering as every post is about something the governor did that literally doesn't affect the city or anyone in it.