It's simply about pride these issues like the mould problem, start at the top. Because they have let all the small things get out of control, no one can be bothered to do anything.
I won't repeat what I think of the dirty shelter in Galactica extended queue or the state of the Obvillian queue line. However, staff at for example Phantasialand would sort out a small issue like Mould, as they feel pride in their park. In my opinion, it's a cultural thing. Merlin is trying to operate towers like Thorpe park/Chessington but towers is so different.