I'd argue that the following are fundamental changes that have impacted the community in a big way:
- Selling 10% of the business to Tencent/Chinese investors
- Firing their community managers in 2015 and not replacing them
- When I first joined Reddit it was more technology focused, now it's all pop culture and memes. Although Tech subs are still plentiful so it can still be that site. (With some effort)
- Banning any Sub-Reddit's that go against whatever the admins mood is on a particular day, or content that no longer fits with their "We have shareholders and need to keep them happy" mantra. Reddit is absolutely not a place for free speech/uncensored discussions these days. Because of both toxic mods and horrible admins.
- Huge increase of censorship across the site in Sub-Reddit's, Posts and Comments
- Users care about the video stuff because Reddit's video hosting is fundamentally broken and hardly works, but they would rather keep it broken because it makes it harder to download videos (DASH)
- The whole new design is anti-user, the site is just masses of white space, super slow, JS heavy and pretty much unusable outside a third party mobile client. The day old.reddit.com gets shut down will be a sad day.
None of this stuff was a problem 14 years ago
Although some of the above comes with the toxicity that tends to come with huge community growth.
You can argue the above isn't significant, but as someone who's been on the site for 14 years, it sure ain't the same place I signed up for all those years ago.
On desktop the new design is much easier to use, it took me awhile to realize, but being able to hit esc and be right back where you were in the story feed is super nice.
Previously you'd get a token in the URL that was some type of state that hopefully let you resume, but it didn't work if you spent too long reading comments and then pressed the back button.
The new reddit UI solved this problem by simply not having users ever "leave" the home page.
The default subreddits are as bad as you'd expect, but there's many awesome smaller ones. Pray your niche subreddit never becomes default.
IMO this is why they keep old reddit around. Some use reddit for bite-sized entertainment; others use it for serious advice and discussion. It makes sense for the site to have two modes.
I'm sure they put a lot of effort into serving their own images and video and placing ads in just the right place for maximal accidental clickage but why would the user care?