1. No submodules. They suck. They don't work with worktrees. They're a pain to work with.

2. Cross-project changes become trivial instead of nightmarish.

3. Testing becomes tractable. Make a change in a submodule? Good luck testing that it doesn't break any of the other repos that depend on it. You essentially turn its API into a fully public API, which introduces a ton of extra work (if you do it right, which nobody does).