In 2018 I signed up for Figma because of the Notion integration (you can embed Figma frames in Notion), and the generous free tier. Notion took off that year as well and I think both profited from another.
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.