ProseMirror wasn't a good fit for us because it's integration (especially with React 18+) isn't quite there. Furthermore, we're also looking into building native ports of Lexical, and given's Lexical's API isn't DOM centric, it allows us to do that.

Lastly, we found ProseMirror was too heavy in terms of bytes for very minimal almost plain-text interfaces where we only wanted mentions + hashtags + custom emojis. Lexical comes in at around 22kb min+gzip, so it works really well for us.