Hostile mobs that can't reach the player will retreat

So I was thinking of ways to easily beat the Warden, and quickly realized you can just walk into a space too small for it to fit into. For example, in the reveal trailer, the player could have easily just stayed in the room he was in while attacking the warden because it can't fit through the 1 wide doorway. You can also just pillar up. Both of these are way too easy and remove the scariness.

This is also a problem for endermen, who are supposed to be powerful and scary monsters to fight but are laughable while simply standing under a 2 block high roof.

My suggestion is to make most mobs that are currently attacking the player but cannot find a valid path to reach them for an attack retreat outside of melee range. If the player hits them with anything while they cannot find a path, they retreat until they are no longer within line of sight, to prevent cheesing with projectiles. They remain hostile towards the player indefinitely, and stand still unless they find a path to attack or take damage from the player, in which case they try to find a new spot that blocks line of sight.

This AI change would apply to most ground mobs that pathfind towards the player, with some exceptions. Ranged attackers like Skeletons and Pillagers don't need this because they can shoot the player even if they can't reach them. And I think undead mobs are too mindless to think about retreating, so zombies and other undead wouldn't retreat either.