> This isn't markdown, but markdown + dozens of extensions,
Yes, if the way you use Obsidian includes dozens of extensions that each use a proprietary format, then it's similar to just using Evernote in many ways.
If you're mostly using plain markdown with only a few custom formats, then it's still easier.
If today, right now, Obsidian stopped working, I could literally open my Obsidian folder in VSCode and still be able to do 90% of the things that I do in Obsidian.
If today, right now, Evernote stopped working, it would take some effort to find a working version, export the files, convert them to markdown or whatever, etc.
I just don't know how you can claim that Obsidian is more effort to use outside of Obsidian than something proprietary.