I’m not sure I would describe that as an issue with the mechanics. The mechanics do exactly what they were designed to do, and they do it quite well. But, I don’t disagree with your greater point; 5e managed to attract an audience that isn’t especially interested in what it was designed to do, and is now stuck in an awkward spot where the audience as fallen in love with the square peg and doesn’t want the corners to be cut off of it. They can squeeze it through the round hole if they tilt it just so, and that’s how they like playing with it.
Indeed, 5e does the square pegs and rectangular pegs pretty well.
It's just that many fans old and new have not been interested in the square hole for a while and are enamored with the round, star, hexagon, and triangular holes.