Some context if you are really willing to discuss:
It’s not realistic proportion or proportion between units and buildings. It’s the proportion within buildings themselves. It’s like a human unit with huge fists yet small arms then one other human unit has proportionally a much bigger head (yet the same height as the others).
And it could be trivially fixed without any changes to the gameplay.
When artists design the looks of giants and dwarves (which are NOT realistic) they didn’t just zoom a normal human being in or out. They need to adjust the body part proportions to make them look more convincing. Same goes here. A “smaller” building should not be a normal building shrunk, but one with fewer but normal sized doors, windows, rooms.