I think I complained about NCIS a bit in another thread but I'll elaborate here.
The first two seasons with Sasha Alexander were actually pretty damn good. The show took itself a bit less seriously than the likes of Law & Order or even its predecessor J.A.G. and the relatively smaller cast (Gibbs, Abby, DiNozzo, Kate, Ducky and later McGee) made for more personal storytelling. Then Sasha Alexander wanted out, they killed her off within a couple of dumb episodes and brought in the single worst fucking character on the entire show, Ziva, who I suspect was probably the creator's waifu or something because she frequently skirted dangerously close to literal Mary Sue territory. Her fanbase was also absolutely insufferable but that's neither here nor there.
Then the plot-lines just gradually got stupider and more convoluted, the cast bloated up with a bunch of extra characters that nobody gave a shit about and the writers just stopped completely giving a fuck around Season 9 or 10. By Season 11, they finally got rid of Ziva after Cote de Pablo threw a tantrum over gender discrimination or some shit in the writer's room and the show briefly picked up for like half a season. They brought in her replacement, Ellie, who was actually kind of likeable and unique as far as character dynamics went but then they shat the bed again and flipped her character completely after the writers realized that her l33t h4x0r skills meant she could solve half of the NCIS cases by herself.
The remaining original cast members like DiNozzo, Abby and Ducky got completely flanderized and then written off and the ones remaining after that like Gibbs and McGee were given personality transplants from week to week. Now the show is in its, what, 17th season and the writers are either bringing back old characters for a temporary ratings boost or outright redoing old plots with the names changed.
Essentially this show is like 10 seasons past its expiration date and needs to fucking die already.