If you don't need that you should _never_ even consider using Unity.
If you are not interested by the underlying tech of any category of computing, you are not a programmer.
I don't know much about Unity, but this gatekeeping ruins your credibility. It might very well be that writing your own game engine is faster than using Unity, but I actually believe that _less_ now after reading your comment. Your argument seems more pride-based than fact-based.
Programmers specialize based on their interests, and that's a _good_ thing. If we didn't have specialization, nothing useful would ever get done. Mistakenly choosing not to leverage prior work in design space[1] can come at a very high cost.
[1] Borrowing a term from "Darwin's Dangerous Idea" by Daniel Dennett (https://en.wikipedia.org/wiki/Darwin%27s_Dangerous_Idea)
Unity has saved me a lot of time and I don't use the skin mesh animation system.
That's an odd thing to say. I've never used it personally. Even if it's used in the majority of games saying it's the "main point of using Unity" is overstating things. It's simply one feature out of many that Unity provides.
> The only option is to fold your shirt sleeves up and build your own engine. It's not that hard really.
Maybe for you. I wouldn't even know where to start. And I wouldn't want to - that's not the level that interests me.