Is room treatment a science?

yes, it's a science. But you can diy, cheaply and simply and hear an improvement/difference.
It's easier to take brightness and echo out of a room, I would think, than the other way 'round.
Having a large rug on the floor helps.
Artwork on the walls helps.
Seating arrangement helps and the style of seating helps too.
I really notice a difference by pulling the curtains across the sliding glass doors. Stops reflection and harshness..