We don't expect people to learn how a piece table, line array, rope, or gap buffer work in order to use a text editor built around one. If you had to understand some editor's core data structure in order to use it effectively, we'd say that editor had a terrible UI and warn people away from it.

We don't expect people to learn what a VFS is and how it works before plugging in a thumb drive. If some OS expected its users to master such arcana as a matter of course, we'd think of it as a mere curiosity - not suitable for practical use.

You don't have to know how HTTP or HTML work to use a browser. You can just click on things, and that's OK! If some browser made you learn what the DOM is and how to manipulate it before letting you into google.com, wouldn't we say "that browser is crap"?

Only git receives this special pleading: "its interface isn't terrible! You just have to learn all about how its internal implementation works, and then you will be able to use it effectively" - as though that isn't just a description of what a terrible interface is.

This is not true at all, and your examples are bad.

You don't need to know how btree's work to use SQL, true, but you need to know they exist and how they can be used by the database.

You don't know how to rebuild an engine to use a car, but you need to know what to put in the gas tank, when to change the oil, when to change the tires, what tires you can buy, how much air goes in them. You have to know a lot about how a car works to operate a car, or you have to pay someone to figure it out for you every time something needs done.

Git is the same. You have to know about how it works, not all the details of how it works. You could hire someone to do everything in git for you like you probably do with a car, but Git isn't a tool for stupid babies, it's a tool for professionals, and frankly professionals should know how their professional tools work.

If you can't be bothered or struggle to understand how your tools work as a professional, you should change professions as you are incompetent. If you think it's better if you don't have to know, then you will be passed by like you are standing still in your career by people who don't have qualms about knowing how things work and therefore can solve lots of problems in a couple minutes you think are too icky to bother to understand and would take you weeks.

(Note: I'm saying 'you' but I'm not addressing anyone in particular with that, so please don't take this as some kind of personal attack.)