Not really stagnated, but poorly managed I'll agree with -- they're changing, but in what I'd consider to be the wrong direction.
Just about every change has been a net negative for people who want reddit to be more like reddit was 10 years ago.
More stuff to buy (awards, avatars), subreddit chat, lower information density on both the site and official app and all that are all things I feel makes the site worse, and many others who have migrated here (or are considering it) probably agree.