I enjoy dnd, and the type of games you look to like to play, so dont get me wrong, but ones we've tended to accept in past that look to just be for genre or narrative sort of purposes (or perhaps game balance, but hard to determine sometimes):Give me an example other that dead horse known as hit points, and we'll talk.
Hard Armour limits (and even dnd novels allowed this to be broken with likes of Ariakas).
Weapon restrictions.
Fully evading area of effect spells when in middle of them.
Hiding in plain sight.
Lightning bolt no longer bouncing, and not being able to be earthed.