Regarding Agents of Shield, I thought the back half of this season was pretty cool and would give it a thumbs up recommendation. I did not like the first half with Ghost Rider but they tied it up very nicely with the season finale.
I almost bailed after the Ghost Rider season, whose quasi-religious backstory was just too ridiculous for me. But I enjoyed the Agents of Hydra season quite a bit (with the caveat that I'm still a couple of episodes away from the end). I'm burned out on superheroes in general except for Shield.
I have a high threshold for discontinuing something. Basically as long as my DVR keeps slurping up episodes of anything, I'll eventually get around to watching them when there's nothing else on. That said, the multiple babies in the latest season of Last Man on Earth finally made me declare to Wife that I was going to delete it from the schedule...and then they brought in Kristin Wiig literally at the last minute. Dammit, it got a reprieve.