I selfhost my own nextcloud for notes and documents that I would like on my phone but not via google.
It is not a google docs/gmail/whatever replacement. They've spent the past few years hardening it and pushing for all the hallmarks of enterprise first software (e.g. making it a complete fustercluck to not have a proper domain name) but you still have stability and performance issues and the occasional upgrade issue that fucks up everything
I would also point out that if you aren't selfhosting, what are you actually getting out of this? You are just spreading your data out to other companies who are often less transparent about how they monetize you.