You kinda have to cut them some slack, though. The original performers had an entire tv series to iron out the kinks in their characters. The latest performers don't have that luxury. Kind of a shame, but remember how Scooter's present performer sounded in the beginning, compared to how he sounds today. They'll get better in time.
Side note, I kind of like it when the current performers voices deviate slightly from the original voices. I like it when they put their own spin on the voice without completely changing the character. Steve's Kermit vs Jim's Kermit for example. (In fact, I rather enjoy Dr. Teeth's new voice.)