The Greeks knew about this problem and it all comes down to maths. It isn't possible to arrange the 8 or 12 notes that make up western music, into equal sized steps - ie separated by a consistent number of Hz.
So compromises have to be made and the human ear is good at this. Orchestral players and choral singers learn to blend their sound so that it tunes with their colleagues and talk endlessly about "colour", "temperature" etc. And this is just one of the things that makes music the transcendental mystery based on hard, unyielding physics that it is.
Electronic "instruments" can't do any of this; they have to be set to play a specific frequency for a specific note. And they will play that frequency perfectly without variation whenever called on. They can't listen (yet - things develop all the time...) to what's going on around them.
But I think what people hate about Autotune is the way it has been used to produce a "beating" effect where the harmonics of a note are played about with so that some frequency elements of the note are allowed to wander producing that (to me) unattractive warbling or dweeble sound.
I think people on this forum probably know how to use Autotune so that it does its intended job without producing that unpleasant (again IMHO) warbling.
We need to listen (LOL) to them more.