I'm surprised git caught on despite mercurial being much superior (hadn't heard of fossil before). Git has the following shortcomings which are major (some shared by other VCS too) 1) UI- terrible, terrible UI 2) Unncessarily complex data model 3) Doesn't scale well to large repos (until Microsoft's VFS- windows only) (and many others...)
If you only push commits to a branch and use GUI tools like Github or Gitea for merging, chances are you're never going to be exposed to anything more complicated than 'add; commit; push'.
Even merging isn't that terrible and while still being painful, git makes it somewhat clear what you want.
The problem is; if you want people to use something else, you need to improve over git in the areas that matter to most people (ie, 'add; commit; push').
Git is terrible but just good enough that improvement over that terrible will be hard to accept for the mainstream.