Don't you rather believe that the reason why Reddit's user experience is worse is that Reddit has economic incentives (e.g. better options for ad placements; advertisers prefer this US; ...) to do so?
Its like no one involved in the design used Reddit regularly. Reddit's best quality was the way it made forums work at scale, but they tried to copy content feeds at the cost of community. That's why old.reddit, Apollo, and RIF are the better experiences for using Reddit - you can engage in community more than just consuming memes and gifs. Certainly a part of that is incentives, but the job of good leadership is to push back and point out that Reddit isn't Twitter or Instagram.
And even if they wanted to make it like Twitter or Instagram they really screwed the pooch by having terrible stability and performance.
Companies often seem to forget that only like 1% of their users typically actually create the vast majority of content. Even fewer create the real quality content that is so attractive to begin with. It is the quality content, not general content that actually creates value to other users of the consumer variety.
So... looking at metrics of what appeals to the 99% of consumer users and allowing that to drive design, to the point where it pisses off that 1% is a ticking time bomb. It's a seductive one though! You can have all manner of metrics that will look good, but are actually catastrophic in a delayed way: 'More engagement!' is easier to conclude from measurements and looks a lot better than 'Signal to noise ratio of quality content to generic content has decreased'. 'This new change makes it easier for non-technical people to sign up or post or consume content' seems great until you realize that's code for 'uh oh, it looks like the voting effects of newer users are suppressing quality content over less-nuanced content and signal to noise has decreased even further'. But those things also temporarily look good: 'more users!' 'more revenue!'
And the social media implosion cycle begins anew as quality users leave in droves to a new platform.
That now redirects to some low-content page with obfuscated numbers that haven't been updated in 2 years. And it's not for lack of updating. The one thing I did learn from that page is that they just hired a new VP of UX, yesterday.
I used to use reddit constantly and they've killed all the useful subs, made the mobile ux nigh unusable, and turned the user based in to a leftwing circle jerk.
So now I barely ever use it.
If anything, the new UI changes are in service of an IPO, not the reason it would fail.