Rick and Morty Season 7 has finally debuted, with fans and non-fans alike tuned in to hear how the show would cope without Justin Roiland. After the co-creator was fired, Dan Harmon and showrunner Scott Marder had the exhaustive task of finding a replacement. It wasn't easy as Roiland voiced the main characters, as well as minor ones like Mr. Poopybutthole.
Source:https://www.cbr.com/rick-and-morty-season7-voice-problem/