There are a ton of parsers out there, which is great, but there is no Emacs-independent set of tests you can run against a parser to figure out if it's compliant. Ultimately, the Org format is what Emacs says it is, and everyone else just tries to play catch-up.
I feel like this is a little bit of a missed opportunity. I use Emacs because I think it's (for me) the best editor that exists today, and it's likely to continue to be the single best editor that exists (for my needs) in the near-to-long-term future. That doesn't mean I'm necessarily pleased about how much Emacs tends to suck features into itself and how hard it is to get them out.
I don't like that the "canonical" version of Org-mode is Emacs dependent. I don't like that when I manage my life through Org-Agenda it becomes needlessly hard to work with other tools unless I sit down and find a partially functioning Org parser on Github that may or may not be abandoned. Yes, Org is plain text, but being plain text isn't good enough, it also needs to be easily parseable into a consistent AST or formal data structure on multiple platforms. I don't like that when I write a tool in Emacs Lisp that I can't run it headlessly anymore, and that it now requires a massive pile of dependencies to run.
The Tern language server was a good development on this front, it's good for language formatting tools to be separate from editors. I wish more parts of Emacs would work that way. But it's not so much of a problem that I'm willing to give up Emacs to in order to cobble together a system that adheres more to the Unix philosophy of being more composable. The lock-in effect is definitely real, it's just that Emacs also happens to be good enough right now that I don't have anything else I particularly want to move to, which makes the lock-in a lot less annoying.
I'd move off of Emacs if I felt like any of the other editors were better, but I don't, for me none of them come even close. Emacs has a huge community and a huge featureset that dwarfs other editors, and it also has this core of flexibility and transparency and extensibility that I feel even "configurable" editors like Visual Studio and Atom haven't really caught up with. But importantly, me saying that Emacs is the best editor around is not quite the same thing as me saying that Emacs is good.
I don't have any regrets picking up Emacs, at all, it was a great choice and it's paid off tremendously, and I think it'll continue to pay off in the future. But I do wish there was a better editor out there.