zzz I just want to make it clear that I totally agree with you that avoiding vendor lock-in is important. For that reason though, I have decided to choose for Obsidian even if I don't think it's perfect (e.g. not being open source) and that's why I stick with core features only. I haven't really used the Canvas feature, but I do use the Graph view and I really love that actually. This however is built on top of the linking of notes, so on note content. It only visualises the links between those notes (which may not be important for everyone, it makes a significant difference to my journalling). The links are built in either the Wikilinks format or the Markdown format (you can choose) so that way you can take the linking with you. I don't really know whether other note taking software offer Graph view functionality, which for me has proven really important, but again, the primary linking of the notes is not lost. You can literally use your content the way it already is. This is really my primary reason of responding here, to counter your previous statement, which is not true for every use case:
Moving off the platform is also not super simple, as I understand it, it involves copy-pasting stuff out of one note at a time, or using third party software.
Do you link notes in Standard Notes? I can't tell whether their tag system is proprietary or Wikilinks/Markdown underneath, so how would it work if you have to take your notes with links elsewhere?
I do think you've given OP good food for thought, but I hope I've added that it's not really a simple black and white situation like you describe. We agree it's very personal. I wish OP best luck in choosing the tool that matches their aims.