What is complex is the hundred features and commands it provides on top of that model.
I strongly disagree.
Let's list just basic git concepts that you're likely to encounter fairly early on: the working tree, staged commits, branches, remotes, stashes, detached heads, tags, submodules, merge conflicts, squashed commits, fast-forwards, rebasing, cherry-picking.
Some of these you could choose to ignore - rebasing and submodules - but on the whole you need at least a cursory understanding of everything on that list to get by without a git angel to get you out of trouble. I still have a person I phone when anything out of the ordinary happens and I've taught git to other people!
I'm also genuinely surprised that people use GUI for git. For merge I understand, but for all other tasks cmdline is easier and faster.
Which is exactly why people want better clients than the official git cli client.
I nearly spat out my drink. Git is many things but those aren't the first two words that would leap into my head.