The whole appeal about reddit is it's not just one "community," it's multiple subreddits with different rules and different types of comments. If a subreddit becomes too negative, just hit the unsubscribe button and find a better one.
You know, I get this response every time I talk about this topic. I really dislike the "well no one is making you use / buy / watch / listen" to something. People can be critical of something they want to succeed. It happens a lot in certain game communities. What if I WANT to talk about politics, in a civil manner? Any sufficiently popular subreddit, just devolves into complete trash.
I definitely agree that many subs - and particularly front page ones - can be a cesspool, although amusingly they don't quite get as bad as just about every news and newspaper site I've seen. But really, /r/upliftingnews is just too toxic for you? /r/changemyview is too negative?
There's lots of great, very low-toxicity subs on Reddit. Abandoning the site because you're trying to discuss political issues - touchy in any arena, online or in person - seems a bit like throwing the baby out with the bathwater.
What you're looking for are strictly moderated subreddits with a clear set of rules. I've had good luck with r/NeutralPolitics and its sister subreddit r/NeutralNews.
Reddit isn't a community so much as a tool for people to form communities. The people who realize this get way more out of reddit than the people who don't.
I've been a part of many forums and internet communities and chat rooms, and they always tend to go the same way:
The people who have been around for awhile get increasingly annoyed by the newcomers and their lack of decorum or 'idiotic statements' or whatever, so that segment of the group starts posting in a new more secluded place and use the other place less and less.
Eventually more and more people find out about the 'secluded place' and it becomes more and more cluttered with 'undesirables', (often a few people from the previous group are now part of the old farts, or have become the new old farts), so a chunk of them break off from that community or forum and start posting somewhere even more secluded. And eventually it happens again. And again. And it's turtles all the way down.
I saw the same exact shit happening in real life too with Meetup.com. People stopped posting stuff to meetup groups because they didn't want certain people to come, then there's a smaller group that's secret from the others, then either some people find out about it that shouldn't or one of the people in the secret group starts acting in a way that the other people don't want to deal with them anymore (for example, one time it was because they started dating someone who was a real jerk), so a new, smaller secreter group is formed, and so on...turtles all the way down again.
The Meetup scenario is depressing. Thankfully the one Tech Meetup I attend every so often is positive.
The meetup thing started innocently enough a couple times (with a couple people I was told explicitly they didn't want certain people to come), it's like 'we found some people we like hanging out with now thanks to meetup and now we're just inviting them over to our place', but eventually they stop posting their normal stuff on meetup and it gets harder and harder to keep the group going.
I was a forum admin for way too long. Kinda glad I'm out of that now. Although now I'm an organizer for a meetup group, and it's not much different.
It's just another example of the tragedy of the commons.