In the modern law&order versions, the CSI-whatever and other police shows, half of the suspect spontaneously confess without a lawyer and the other half confess after borderline torture. And the forensic analysis use magical methods that would not be believable even in Start Trek.
How about "Frasier"?
It was remarkably consistent throughout all 11 seasons, after the first handful of episodes established the characters.
To give a somewhat different perspective, I personally have a "5 season rule." Maybe it's more like 5 seasons +- 2 or something like that depending upon the show. Some shows aren't that interesting once their quirkiness wears off and other change things up enough to keep going longer.
But whatever the exact number, I just weary of the characters, the format, the style, etc. after a time of just about any show even if it doesn't decline in "objective" quality. I'm definitely not a person that wants some beloved series to go on forever. Generally if something has gotten a few seasons under its belt and wraps up in a reasonable way I'm very happy to let it go. (And this is truer than ever today when there are far more good shows on television/streaming than I watch.)
I don't find that surprising. The audience doesn't stay the same for 10 years either.
We cut our cord about 8 years ago and our TV has been limited to streaming and Netflix (DVDs too) My observation is that a great show seems to need 2 to 3 seasons to really find their pace, rhythm, and get it figured out. This is changing with the short season episodic content that everyone is doing now but network shows sort of need some time to find themselves. Beyond about season 7, they all fall apart in some way. I really can’t think of anything that lasted 10 plus season and wasn’t effectively a different show from s1, only the names are really the same; definitely the feelings it gives you will have changed. I really only watched Simpsons occasionally during the first 3 seasons, it’s hard to fathom it having anything in common with then now.