Why do all the elevator shots suck?

Watching this for the first time and I have to comment on how badly the elevator shots look.

There is one at the beginning of the movie when the two executives are going up on the elevator and the city is in the background. This shot looks terrible! It's so obviously faked/rear projection.

Then at the end when Russo and Estevez are riding it, again, terrible. Even in the first shots where the city isn't even in the background, it's just a blue backdrop. Looks totally terrible.

What technique did they use that made it look this bad!?