it takes less work
this is correct. Shovel knights and especially undertales graphics are simple.
You are making alot of assumptions.
First I started making games with pixel art like rpgs, jump n runs and space ship shooters.
Then I went to 3d which took years to make a single game.
And then back to 2d vector because you need a team for 3d games.
And about your argument metal slug: Yes, these animations in this quality are still easier to make as pixel art than in hd sprites like skullgirls. Pixel art is art generated pixel by pixel, not by drawing. If you ever animated a pixel art explosion you will see how easy and quick it is to do. Especially because you do it in one go. No predrawing very linear. Pixel art is the easiest way to draw graphics for a game. And go the fuck away with your fucking assumptions. And make a game before you insult me and try to use the little brain you got and try not strain it...
what a simple creature you are, that you get hurt, by someone having experience you don't because you are too lazy or stupid...