MCU Villains: Why so controversial when criticised?

I don't really think you understand this whole thing. You don't seem to grasp what makes a good villain here at all.

There's a reason why Hans Gruber is iconic and considered one of the best villains and why Kaecilius is considered a weak villain. That's polar opposites, therefore saying they are the same would automatically be wrong. If you can't see that then that's just your problem alone as everyone else can seem to see the reason why.

A character doesn't need to be deep or have an extensive backstory to be a good villain. Darth Vader in the original Star Wars did not have that and yet he also is an iconic villain and better than all of Marvel's.

Even The Terminator. He was a robot who didn't even have that many lines in the movie, played by an actor who isn't that great of an actor and yet he too is an iconic villain that is far better than any of Marvel's villains.

Do you even understand why that is even considered?