Personally I thought it was a pretty intense episode. Yeah it was a bit frustrating I guess not to see who Negan killed... but that's kind of the job of a cliffhanger and I'm perfectly fine waiting. I mean the style of the show has been firmly established by this point, so you'd think people would be a bit more used to it.
...or tired of rinse and repeat. Three season-ending cliffhangers in a row? Terminus in 4, peaceful Morgan showing up in time to see Rick murder Pete at the end of 5, and now Negan at the end of 6. Even the 1966-68 Batman--famous for cliffhangers as part of the format for nearly 100 episodes--eventually broke that format (no matter the cause). I think some would feel the danger, and itch to see season 7, if they were left with a guaranteed, major death, leaving no doubt that Negan..no, the series meant business. After that, 7 could hit the ground running with whatever Negan forces on the group--perhaps a slight time jump as Rick is forced to return to ASZ, explaining the new state of things, but heavy with a tragedy--one that for the audience--shared with him over the summer break.
And be willing to sit through some of the slower buildup before the really crazy stuff happens. And for my money that wait has always been well worth it (although I guess it helps that I've never had a problem with the slower and quieter "filler" episodes and usually enjoy them as much as the more action-packed ones).
I do not think its about fans having a problem with slower episodes, either, but about avoiding the season ending tease over and over again. Personally, my favorite season 6 episode was "Here's Not Here," the Morgan flashback episode, because it was serious character development, rather than other characters walking in circles, waiting for the creeping Big Bad. Unlike some whiners, I loved season two--yes two for the same reason--serious character development which set the important relationships/identity for the rest of the series, and for zombie action lovers, the season ended with a mass zombie horde battle (and even more character development). Best of both worlds.