A lot of drummers are cons. Not cons as in criminals, but they're conning the public by making them think they can play. A really good drummer only comes around once in a lifetime. Neil Peart? Nope. John Bonham? Overrated. Charlie Watts? Average. Keith Moon? Inconsistent. Dave Grohl? BS.
You don't know what you are talking about if you say Dave Grohl is not a great drummer. What even is your criteria? Because you say he is not? He has more awards than anybody. He has been voted greatest drummer by most of the best musicians in the business. While I don't think there is any BEST drummer, the fact that he is acknowledged as amazing by fans and those in the know, may make you re-think that comment.