Matthew Waterhouse wanted it. #JNTDidNothingWrong
It deteriorated once Hinchcliffe was fired because of Mary Whitehouse's autism and Graham Williams let Tom Baker mug instead of act for three years and hit rock bottom in Season 17 when Douglas Adams decided it was more important to non-consenually pepper his writers' scripts with dumb gags than make actually good stories. It's no coincidence the show suddenly got better the very next season when JNT and Bidmead took over and actually tried to make good sci-fi instead of letting Tom yelling "arrrrghh my everything" off-screen and throwing tree branches on set. The problems really started when JNT hired Eric Saward and Saward decided to channel his writing talents into making generic military stories on a BBC budget and even then it didn't get bad until S21 with trash like The Twin Dilemma and Warriors of the Deep. Saward is the real villain of 80s who. He was an edgy faggot who desperately wanted to gargle Robert Holmes' balls and did that
infamous interview with Starburst where he blamed everything on JNT even though he hated Colin Baker, wanted to kill The Doctor off so he could focus on generic mercenary characters and wrote Attack of the Cybermen under his girlfriend's name because of a slapfight with Ian Levine. Again, it's no coincidence the show got better once he fucked off and Andrew Cartmel stepped in and actually commissioned good scripts since he knew what he was doing.
tl;dr JNT was a literal faggot but his only issues were liking young boy's buttholes a bit too much, wearing Hawaiian shirts and being too hands-off while the moptop edgelord was in charge of scripts. S24 > S17 fight me.