In order to fulfill Chambers leaving the show, the Grey's Anatomy team decided to have Alex leave his new wife, Jo, behind without notice so that he could reunite with his ex-wife, Izzie, and help raise their kids together. Since Chambers filmed his last episode in November 2019, he wasn't present during the episode where Jo, Meridith, Richard, and Miranda receive their goodbye letter from him. Fans weren't particularly happy with this ending. Showrunner Krista Vernoff even spoke about the negative reactions to Karev's departure.
"I believe that there would’ve been at least as big an outcry if we had killed that character off-camera, and those were our choices. It was kill the character off-camera, or come up with some believable way that he gets his happily ever after," she stated in an interview with Deadline.
Thoughts: I know Justin Chambers was ready to leave the show, and obviously, it wasn't expected for him to be on it FOREVER, but the way he was written off just hurt years of character development, IMO. Season 16 Alex loved Jo so so much, and his exit just seemed like something Season 5 Alex would do. While it was noble for him to leave to raise his kids (that he just found out about, BTW), I still wish things played out differently. He would've never left Jo (and Meredith) like that without even saying goodbye (face-to-face), but for some reason, that's exactly what he ended up doing.