I think the biggest issue is dealing with very large code bases, like the code for a mid-large size company. You either go with a monorepo and deal with slowness, Windows-only optimizations and bare minimum partial checkout support.

Or you go with submodules and then you have even bigger problems. Honestly I’m not sure there’s really an answer for this with Git currently.

The partial checkout support in Git is getting improved. Take a look, maybe it now solves your problems.

Support for large repositories via scalar works also for Linux (though not everything is ported; as main body of work on supporting large repositories was created to deal with the size of MS Windows repository, it started with Windows-only support / optimization first).

There are alternatives to submodules, like https://github.com/chronoxor/gil

Aside from the obvious UX disaster, Git has some big issues:

I find this blend of claims amusing. I've been using Git for years on end, with Git LFS and rebase-heavy user flows, and for some odd reason I never managed to stumble upon these so-called "disasters". Odd.

What I do stumble upon are mild annoyances, such as having to deal with conflicts when reordering commits, or the occasional submodule hiccup because it was misused as a replacement for a package manager when it really shouldn't, but I would not call any of these "disasters". The only gripe I have with Git is the lack of a command to split a past commit into two consecutive commits (a reverse of a squash commit), specially when I accidentally bundled changes to multiple files that shouldn't have been bundled. It's nothing an interactive rebase doesn't solve, but it's multiple steps that could be one.

Can you point out what is the most disastrous disaster you can possibly conceive about Git? Just to have a clear idea where that hyperbole lies.