Ok, so you agree he might not be as powerful as the Emperor. Then why is it so hard to understand how he might not be able to do something that the Emperor can do as a result?
Because Darth Vader is a master of the Dark Side. Let’s say if Vader in the OT was as competent as Darth Maul, Kylo Ren or even the Inquisitors from Rebels I can understand why you would say that as they are nowhere near Sidious but the gap in power between Vader and Sidious isn’t that big to have certain abilities be completely alien to him. Higher proficiency maybe but not entire abilities.
It’s like saying I’m stronger than you but I shouldn’t be able to lift more weight than you.
It’s a little more complicated than that but I see what you’re trying to say.
EDIT:
Nostalgia has to do with it in Dominic and Impscum’s case. Maybe not yours but theirs.