Well that's certainly fair. However in the case of both Joplin and Zim (and probably others), notes are either stored in or can be trivially exported to plain-text formats. Joplin's native, lossless backup format is just markdown in a tarball. Both are also open source.

Standard Notes might have a good chance of lasting that long. they seem very focused on the long term. can't remember the specifics now but I think there's a faq on their site where they explain their philosophy