I thought the latest season was very funny. And, even knowing exactly what they did with the voices and why; I didn't notice a difference. I'd say Harmon is right.

Incidentally, Justin Roiland also voiced one of the main characters on Solar Opposites, so they had to replace that one too--which they did in the funniest possible way.

The last few seasons have been absolutely awful, but this newest one has had a few of the best episodes in the entire series. There's one writer in particular, and I forget her name who's been churning out absolute bangers. Whichever one wrote the spaghetti and dennys episodes