The last good season was Season 5. The show died when it started to take itself too seriously. Too much back and forth. For an entire season they are in revenge mode and then all of a sudden at the end they go over the top full fledged PC mode and start preaching niceness again. Its lame. They do it over and over. We get no payoff when they finally gain control over the Negan. We get more PC preaching. Sucks.
The show was great early on but to be honest, it seems that when Greg Nicotero took over, the show sucked. He is one of the best effects guys in the biz but he is no director. If you like shows that run around in circles then this is for you.