I switched from Keep to Obsidian as well. It depends on your goals. For me, I was saving things in Keep that I wanted to have forever and I don't trust Google to operate the service forever. The exported data is also not super portable. And there are things I want to save that I don't want on a cloud service. So I switched to Obsidian which gives me a simple and portable file format, privacy, and I trust myself to keep those files safe more than I trust Google.
For me, plaintext (like Markdown) is a strength over proprietary or binary formats and I've accepted the tradeoffs. It's the primary "good reason" I use Markdown. I have confidence that text will always be readable in the future even if I don't have the app that made it. Secondarily I find most word processors overkill with toolbars everywhere and I do not like using them.
Same experience... There's a lot to like about notion and I chose it over everything else and am using it professionally and personally. But the sluggishness is really starting to bother me
It's a nice wiki with some interesting database features (a la airtable). Writing in it is pretty nice because it's basically markdown.
I'd stopped using it because it was too easy to outgrow the free plan. Now with unlimited pages I'll give it another shot but I'm still not sold on its benefits vs storing all my notes locally in plain markdown files.