Well, I finished watching the remaining seasons of Family Guy. My conclusion is that the series has descended from a platform for edgy hit-or-miss jokes into just another mediocre cartoon.
As with earlier seasons, Family Guy has potential but almost invariably falls short. Take, for example, "Brian & Stewie", the climactic 150th episode. It's essentially a one act play of Seth MacFarlane talking to himself for an hour. It was a brave step into philosophical territory, and I wanted to like it. I hoped it would finally redeem the series. But in the end, Seth MacFarlane is no Samuel Beckett, and the episode fell short of the insight I longed for, in favor of TV-flavored pseudo-depth.
This is a good representation of the latter seasons in general. They try to provide what the earlier episodes lacked: focused storylines and greater character development. The amount of cutaway gags and side plots per episode decreases dramatically. Yet while this change has the potential to allow deeper character development and more interesting stories, the attempts fall firmly into mere mediocrity. For one thing, the characters simply lack the consistency to develop in any meaningful way, often changing their personality at the drop of a pin to suit the latest gag. And the plots themselves are insipid and predictable - typical TV trash. It often seems that the writers ran out of ideas and turned to formulaic television tropes. Take a formula story, pepper it with old jokes stolen from earlier seasons, and there you have a later-season Family Guy episode.
Now, that's not to say Family Guy is without moments of true humor. It even made me laugh a few times! But in general, the little merit there was to Family Guy is almost entirely absent from the latter episodes. By now I'm just relieved to be done with it.