Maybe it’s expecting too much that a TV series remain in your heart for 17 seasons. I still enjoy The Simpsons (starting its 31st season) and South Park (starting its 23rd season), but both the cartoon format and the nature of those shows gives them a lot of latitude in exploring new ideas while remaining true to the show.
A drama, like NCIS, which I’ve rated as my favorite TV show for well over a decade, is more restricted. It’s harder for a drama to find new ground while remaining true to its nature. That can lead to stagnation, viewer fatigue, or, in some cases, “jumping the shark.”
Which is all to say I’m very disappointed in NCIS, season 17.