I wouldn't be too sure of that. I remember reading libc source and thinking "wow this is so complex it must be written by geniuses and be really well optimized". Only years later did I hear that a lot of it is shitty for pretty much no reason and there is a lot of low hanging fruit to pick.

I mean gcc is really advanced and it does work very well. But if there is something that intuitively seems bad in there I wouldn't assume it's that way for a really deep reason beyond my comprehension.