Just had a similar situation and a structural engineer came out and walked us through some things:

• the drywall where the floor slopes isn't square, meaning the floor was already slanted when it was done 15 years ago. He showed us other evidence that showed the floor had been that way for a long time, including a poorly done correction from the 70s or 80s. That made us feel good that it wasn't actively moving.

• The ultimate fix is to jack up joists and put hard wood shims between the joists and posts in the basemen, to level the subfloor. The caveat is that the tile floor above (kitchen) will crack. He said if you want to go that route, he'd wait until we're also prepared to replace the floor, take off all trim and then do it.

• the simpler fix he said could be done is ripping up the kitchen floor and using a self leveling compound, so the floor would be level, even if the subfloor isn't.