A slow spiral into irrelevance because of lots of small bad decisions. At one point, Reddit felt like a lone champion of free speech and conversation in a sea of buzzfeeds.
I think they've moderated the website into ruin. They've put a lot of energy into silencing certain kinds of voices/opinions while promoting others. What's left is a very liberal echo chamber. All of the seemingly worst ideas from the left are stated as fact and voicing a dissenting opinion can quite literally get you banned.
r/antiwork and r/latestagecapitalism are the most egregious examples of this that I can think of. But the attitudes held there have leaked into 99% of the other subreddits to some degree.
For the record, I lean left. But it really sucks to no longer have a town hall where both sides of the aisle can discuss things as adults.
If there's one takeaway, I think it's some flavor of: Don't overmoderate/show favoritism. You can't have yin without yang, or salt without pepper.
What made Reddit awesome was the discourse. Maybe they never realized that this was the secret sauce. That is, the clashing of ideas. And so they didn't cultivate that. Today, outside of a handful of niche/hobby subreddits, it no longer has anything close to educated discussions.
Reddit has subreddits on the right and left that will ban you for disagreeing, or even for having made a comment in a subreddit they don't like. That was theoretically always possible, but at some point people decided such a policy was a good idea.
I personally think a misstep of reddit's has been relying so much on volunteer moderators. Why are people willing to put in so many unpaid hours of labor? Apparently, the answer is sometimes because they have a political cause they want to promote.