Both
@pyf and
@Dr Super Good are spot on regarding the facts about WC3's history with aspect ratio.
@Wrda, I think your judgement comes from a personal preference that you're used to, and that has unintentionally been twisted into something you feel is fact.
The game was created to be 4:3, but later, we were given the ability to just stretched it to fit modern screens. The models / UI / everything are not "thinner" with this update, they are there true size. It's just that they are
no longer stretched. What you think is the normal size is actually the complete opposite, only because you, like many others, have been playing a stretched version to fit our modern screens.
Now if it came down to personal preference rather than trying to prove that this change Blizzard did is wrong, I would kind of see the merit in that. But in the end, that preference comes down to what you were used to (nostalgia) as opposed to what it is supposed to be with objective reasoning.
About the black bars... they're just black bars in the menu. You don't have to do anything about them, they don't give a disadvantage, they don't obstruct. I mean I guess people can say it's ugly, but it's kind of obvious that those would be temporary. It even says in the patch notes that the fixed aspect ration was removed temporarily.