There was so much focus on Olivia in S15 with the Lewis Arc and her therapy sessions and in S16 with Noah that the writers failed to write positive mini-arcs for the other characters. If Amaro is "damaged goods", then it is the writer's fault. Sometimes you need to have a character experience loss so that they can grow; I think most fans understand this. However, I feel that both negative and positive growth are essential for a balanced character. Even though heartbreaking and terrible things have happened to Olivia, she was allowed to grow. Amaro, on the other hand, lost but never gained...for three seasons straight, I might add! When he did gain something positive, like finding out about Gil, the writers didn't do anything with it. If you keep writing a character that way, eventually the ink will run dry on your pen when it comes to fleshing out said character. S15 was bad for Amaro, but there are things they could have done in S16 to bring more depth to his character and to give DP more material to work with. Why not have Cynthia get shot and have Gil move in with Amaro? They could have explored the father-son dynamic in a big dramatic way. Or, why not put Amaro with Cynthia instead of with Rollins? It seemed like they weren't at odds with each other anymore by the time of the S14 finale. Rekindling an old romance could have been interesting. I just don't understand the need for all of the Olivia/Noah scenes when Noah is played by an actor who can't emote. Noah is cute and I'm happy that Olivia is finally a mother, but that kind of thing doesn't make good drama. To be fair, the writers did give Amaro (and Rollins) some big character episodes, but when they did, there usually wasn't any follow up and that was sometimes frustrating for fans.
My guess is that Danny Pino would have stayed if he had felt that there was more meat to extract from his character.
Surrendering Noah felt like a series finale to me and I may end up treating it as such. I am sure there will be some interesting stories in S17, but I don't know if I will return to watch.