Always consider the longterm effects of your DIY projects before undertaking them. For example, if you Humans do not enjoy tripping over lounging Felines on your way upstairs and down, perhaps you shouldn’t have installed cushy carpet stair treads.
Swearing about the current situation, even at length, solves nothing.
Now the stairs both belong and are desirable to us, the Cats.
Humans, what did you expect would happen?