Let's imagine a supernatural creature that can walk off all damage unless their heart is hit. (think Mr Sinister. The damage is done, it's just not lethal) These creatures exist in modern times, have similar anatomy to us, and any damage to their heart is as lethal as it is to us.
Modern armor is heavy, bulky, and does a poor job of protecting it's wearer from direct gunfire. Even a poorer job against military grade gunfire. Now let's imagine that only the heart matters. Maybe we don't need the large vest anymore? just a single frontal plate made of a much tougher, heavier material? Would anything reasonable for humans to wear be able to stand up to modern assault weapons?
Let's also assume that the shooters know what they are doing. They know where to aim, and if the armor becomes part of "the meta" they would adjust their ammo. Would it still make sense to try to wear protection if you were most likely to face FMJs or whatever the proper counter would be?
Notes. I understand that people can be shot from other angles, but let's assume that most gunfire would be from the front. (that does not mean that if you think that fire coming from the front would actually hit from other angles you should not mention that) I also understand that nothing is going to stand up to a 50cal, let's only consider normal weapons up to assault rifles