Stagnated? Really? I think they have had some really great ideas, though it is true that some products suffered from some serious issues and missed the mark. If a new idea that pushes the envelope does not gain traction, I don't see that has stagnated artistic spirit. It was a gamble on an idea that some really loved, but not everyone did. Every book they've published has been good for somebody, even if it isn't for me, specifically.
Wild Beyond the Witchlight and Radiant Citadel were both delightful, groundbreaking publications. One being family friendly that can be resolved without combat (if wanted), and the other being all brand new lore content that introduces more about the Ethereal Plane, and alternate material planes that celebrate diverse setting seeds.
Strixhaven was a bold attempt at something new for a younger audience, and to me it looked like an attempt to capture CW tropes of teen academy romadramady (romance/drama/comedy), with jump-cut episodes rather than an organic day-to-day story. I like the idea of the setting, but I used it as inspiration for my own story, rather than utilize the adventure/mechanics of the published adventure itself.
The Book of Many Things is amazing, and offers so much variety that can be taken or left as needed.
They do push the envelope, but not all new ideas are going to sing to every gamer. And then there are the occasional serious missteps, like Spelljammer not having decent space combat, and messing up the Hadozee. It could have been good, but they missed the mark.