Billy West is 72, and Katey Sagal is 70. They're trying to voice 20yo's. There is a limited amount of content we're going to get out of them. I'm also sure the budget wasn't was it once was for the VA's or the writers.
I'm happy that we're getting more content. Even mediocre content has gems in it. I do wish they'd stray away from current issues as it takes them so long to produce episodes at this burn rate that the content is a bit aged by the time we're watching it.