When RPGs were far simpler and your enemies were just a bunch of pixels with no voice lines, it was easier to ignore stuff like the enemy group being made of spiders, goblins and ghosts fighting side-by-side.

But as games evolved, moved to 3d and the enemy stopped being "mobs" to be people with motivations and dialogues you start to also expect them to behave more human-like. So when your Avatar of Death incarnate walk around mounted onf a T-Rex while holding Excalibur on one hand and a BFG 9000 on another those street thugs would stop bothering you.