Is notion still being developed? Seems to have stagnated and feels like there’s 0 investment now. It’s getting slow and buggy.
They are not getting investments anymore AFAIK, but they're profitable because of the paying users.
I don't think you have to add X features every hour to stay relevant. The software is pretty powerful at this state already, and I might be discovered 15% of its capabilities probably, despite using it relatively heavily.
Did you open tickets for these? Some Notion developers frequent here I believe, maybe you can reach them if they provide contact information?
I always found it beneficial to reach-out to provider/developer. The results were not positive all the time, but at least I managed to add an entry to their bug tracker, and the problems are solved 99% of the time, after some time.