I was an early reddit user from before the time subreddits existed. Much of the user base, including myself, were asking for tag functionality, but the subreddit concept was introduced instead. I guess they needed a way to moderate tags, and that was their solution. Decades later, they told those same mods to go fuck themselves, so maybe they should have just used tags in the first place like they clearly expected subreddits to act.
Just in time for the EU to also force third party app stores through, and X attempting to make one sounds plausible even if they get nowhere with it.