Yeah it's been requested by many. But I don't think refs would be comfortable with that because VAR probably isn't sure in many cases, like in Dembele's case.
So they're probably like "hey man we can't clearly see here in this short amount of time, just go with your initial call".
And then the ref is probably like "aight dawg they've scored plenty goals so far anyway, we should call Dembrook off here".
And then they do their best to get a fabricated picture of the offside.