Not so much that you’ve missed something or are mistaken, but Reddit is likely promoting those subs because they’re some of the only active high quality (I.e. not bots/astroturfing) ones left.

Not going to go through every example you gave, but the specific sport and team subreddits represent live and ongoing content rather than reposts from a decade ago, with many fans, strong communities, and nowhere else really to go. Consider the decline of traditional, non-steaming live TV networks, where at least here in the US, 98/100 of the top rated events people are still watching the old fashioned way are sports. Same thing.