And in any case, the "merge" part would still be up to the app. The data structures will always be able to merge, sure, but the app could still throw up a dialog box on wildly divergent changes saying, "Hey, some crazy stuff happened here—want to look it over and commit manually?" (Where "commit" means generating new changes to overwrite any undesired changes, since it's not possible to literally undo.) You could argue that we've simply implemented ad-hoc coordination protocols in the app layer at that point, but IMO, that's exactly where they belong in cases where there's no authoritative store for your data. (Which is really the case with mobile, offline-first development.)
For example, I think the CRDT approach is probably applicable to most examples of interactive editing, where incorrect conflict resolutions will happen near a point of focus for one of the editors and can be quickly and easily resolved.
If you have wildly divergent documents however (again depending on the document type itself), this is not really the same case, and it's much more likely that a human will need to create a resolved document by consulting the two parent documents.
Is there really great utility in automatically merging wildly divergent documents? Being able to send your queued changes and agree on a new state of the world is lovely, but for most of the circumstances I can imagine the ideal new "state of the world" is "please fix this merge conflict", not "here's my best guess at a reasonable state based on the semantics of some data structure."
Maybe it's domain specific. Maybe in code you want merge conflicts and in some kinds of rich text docs you just want a best-guess auto-merge. Even then, though, I think it would depend a lot on what the document is for. Maybe blog posts and company culture docs should get auto-merge and legal contracts should get merge conflicts.