Correct you are. Andy was the weakest major character on that show. Had it not been for Barney, Floyd, Gomer, and Otis; TAGS would not have been the classic it is today. Even the secondary characters were better; the Darlin's, Ernest T Bass, etc.
I would rate Andy right alongside Raif Hollister and Miss Clara on the scale of importance. All 3 were better than Howard Sprague, though.
Take that shit back right now! Raif was far more important than Andy. If not for Raif, then Barney with his bad voice would have been the one to sing in front of the Ladies League. What a disaster that would have been for Mayberry, it would have never recovered. Raif saved Mayberry and that is more than Andy ever did for it.
Best role he ever played was in "A Face In The Crowd". He plays the asshole, which is I understand is actually how he is in real life, so the performance was natural for him.