The Walking Dead may be afraid to kill off its major legacy characters, and is opting to find other ways to write them off the show. Granted, the AMC series didn't seem to have this problem when it let Negan (Jeffrey Dean Morgan) murder Glenn (Steven Yuen) in the season 7 premiere, or when it let Carl (Chandler Riggs) get bit by a zombie in season 8, but things have apparently changed since then.
Seasons 9 and 10 featured the exits of three of its oldest characters: Rick (Andrew Lincoln), Maggie (Lauren Cohan), and Michonne (Danai Gurira). Michonne's exit happened when she found out that Rick may still be out there somewhere. She decided not to return to Alexandria or the Hilltop.
Recently, The Walking Dead has hesitated to kill its oldest characters, but why? First of all, controversial move to kill off Carl.
The last two seasons have made it obvious that The Walking Dead hasn't been afraid to kill off its characters, but what's important to note is who the show is willing to drop. In season 9, the Whisperers killed multiple characters; however, none of these casualties, not even Tara (Alanna Masteron) or Whisperers took the lives of three more characters, but all of them were only introduced in season 9.
The writers avoiding killing off The Walking Dead's oldest characters is not necessarily a bad decision. Rick is never coming back, but with Maggie, for instance, The Walking Dead can maintain a connection to its past, by keeping these characters alive. By not killing them, the option remains for them to come back. This is something that the writers may want, especially because as the show and the cast evolves, there's always a chance that the series can become unrecognizable over time. AMC may not want to alienate the show's oldest fans.