I don’t see why using submodules as a package manager should excuse their endless bugs.

I don’t know what are these “endless bugs” you’re talking about. Submodules might have a UX that’s rough on the edges, but there are really no moving parts in them as they basically amount to cloning a repo and checking out a specific commit.

Do you actually have any specific, tangible issue with submodules? Even in the cases you’re clearly and grossly misusing them