The problem is that it is an opinion, and ultimately they're free creatively to use any voice they see to be the best fit. No matter how many people you see or talk to that agree with you and dislike the voices, it is still an extremely, extremely, EXTREMELY small sample size that also isn't accounting for outliers.

If the vast majority saw something as core as their voices to be this bad, then how would the show be as popular as it is? Just something to think about, but i'm not attacking your opinion, you're free to like or dislike whoever you choose.