You look at most naval vessels and the furnishing is almost an afterthought.
I think federal prisoners would be writing their congressmen if they were forced to eat in a Naval vessel mess.
I actually didn't think about the spiral staircase, it seems so out of place, I have to wonder if there's an inside joke that I'm not getting.
It would be awesome to see one of the cruisers and its like the Enterprise D TNG with luxurious cabins and soft carpeted bridges and something like the 10 Forward hotel bar on the enterprise and have the crew of the Orville in shock when they see it.
Then have them go onboard of a small exploration vessel and have it be incredibly crappy with turned over cargo crates as chairs and tables made up of empty cases of beer.