> The filesystem is super slow, and git commands take multiple seconds.

Ugh, this is a known issue in WSL if you try to use git on the host operating system (/mnt/c/Users/path/to/repo)... there are cross-system file system virtualization issues in WSL2 when reading from the Windows hosts.

Workaround is to have your git repos within WSL itself (~/my-git-repo) to have native performance.