That's what I switched to. Mainly because Ansible Galaxy collections don't pull the submodules when fetching the collection.
It is a great and more ergonomic alternative, can't recommend enough.
In practice it is POSIX-only, which is not viable in an organization where Windows needs to be a first class development and deployment platform. Running under cygwin or WSL is a non-starter for a number of reasons (I've done that myself for tooling in the past, after which I would never impose it at an organizational level).
git subrepo is what I chose to include a "core" library of functionality in a number of repositories.
Works fairly well, the main thing is that git treats all the files in the subrepo the same as any other files, so no surprises.
>This command is an improvement from git-submodule and git-subtree; two other git commands with similar goals, but various problems.