I have no answer when it comes to American shows like the ones you listed. The “remaining audience” answer is probably the only logical one easily grasped. I personally haven’t watched such shows in decades because 1) they stopped being funny a lifetime ago, 2) they all became agenda driven.
I know that there is a huge Seth McFarlane fanbase through out our communities here thanks to love of The Orville, with favorite YouTubers like Doomcock and Nerdrotic among them. I personally say fuck Seth McFarlane for one reason and one reason only that to me is unforgivable. Back during the 2008 election, during the annual Family Guy Road to Wherever spoof they would put Stewie and Brian through, the pair went time traveling and ended up in Nazi Germany. Well…on the run from Nazis, Stewie stops and lifts up one up the lapel of a fallen Nazi, and underneath was a McCain/Palin campaign pin.
Right there. Seth McFarlane was calling people he disagreed with politically Nazis as far back as 2008. Proto SJW bullshit, thank you VERY much. So everyone can fawn over how great the Orville is…I don’t give two fucks, because McFarlane was doing SJW bullshit as far back as 2008. I quit watching Family Guy immediately because of that shit, and I refuse to watch or support anything Seth McFarlane for the rest of my life. So if we’re going to call out SJWs for calling people Nazis, then McFarlane does not get a pass and should be called out too, I don’t care how much The Orville is filling your Star Trek wants hole.
As for Anime that never ends….anime will go on as long as there is source material. Detective Conan and One Piece will go until the mangas end.