Re: Am I a terrible drummer?
Mr. Zurgman, the optimist in me is saying that perhaps your MD likes you and is trying to better you. It sounds like he gets the fact that the drums can make or break a piece, and perhaps he is trying to steer you down the right path because maybe he sees something in you that can be developed. I would take his critique as positively as possible, and please, don't even think about the quitting thing.
From the info you provided, what you are playing...it sounds like you aren't doing what he is looking for, at least in some places. If you can learn to take comments that are designed to be helpful to your playing...even if the delivery is less than optimal...that skill will serve you well. I suggest recording your practices so you can hear what's going on. Things that don't work should be readily apparent. Taking that recording to the MD for his opinions can only help you, and it will show him initiative on your part. It will give you a chance to really discuss any problem areas, and since you are not playing and have all your brainpower to analyze things, maybe his comments will make more sense.
Learn to use criticism to benefit you, and keep it positive. An open mind and a willingness to hear and use criticism is a great skill, and not limited to drumming. A positive attitude, even when someone is questioning your choices, is admirable. So try and be that guy.
I always say, hey I'll play whatever you want. If someone has an intelligent opinion about the drum part, it's in your best interest to try what is being suggested.