But just standard moderation of content? That's absolutely necessary. Without moderations subreddits degrade into memes and low effort comments. You only need to look at web archive to see the quality of many subreddits vastly decline as they got big.
As a mod of a default subreddit, we remove joke comments and image posts. And it's not like it's a new thing, we have always done that. And the quality is still far from perfect, but it's much better than other subs.
Sometimes I click on the comments of a reddit post looking to see more discussion about it. And instead it's just a bunch of jokes. Often by a handful of people that lurk in the rising posts, and make sure they get their comments there first, and so beat all the other comments (reddit's comment sorting algorithm is god awful and easily exploited like that.) Even if they don't have anything to say, or any insight into the subject.
Another problem is there are two different types of users. "Serious" users, for lack of a better name, and "entertainment" users. The users there for entertainment upvote images, jokes, etc. Serious users are looking for discussion and debate and whatever. These two categories aren't easily separated and often mix. The users looking for entertainment often take over subs about serious subjects, e.g. worldnews.
The top posts become whatever pleases the lowest common denominator, or requires the least effort to read. Short articles are easier read the long articles, and images are even easier, and provocative headlines even easier. So image posts and headlines like "mildly important official says something politically unpopular" take over entirely.