Because zoomers who never played a real N64 in their life take one look at it and repeat the braindead "LOL three hands!" meme without knowing that you was never meant to use all three parts of the controller at once and that even the manual mentions this. They can't conceive that the controller had different ways to hold it and having an analog thumbstick was different and experimental at the time.

As for Gamecube, like another Anon said, just LOOK at it! It looks like concepts from several different controllers were tossed into a blender. A giant A button in the middle, orbited by a smaller B button and kidney-shaped X and Y buttons. Having two shoulder buttons on one side but one on the other. Two different styles of analog sticks, with the second being considered """button""" "C" but is actually an analog input, and a d-pad made for ants. Anyone who thinks this is a good controller design has brain damage, which is probably not surprising that Melee players think it's the best controller ever made.

Sadly, it's mostly the N64 controller I see get hate, not the GC which deserves the hate but seems to mostly get praise.