Chas...
I don't believe it is the inability to learn or the lack of coordination as a result of age. Rather, it is the lack of patience as we grow older.

I'm willing to bet that if you took drum lessons from a good teacher and practiced the rudiments regularly, you would find a lot of satisfaction with your new drum kit.

Up until the late 80's I played drums in various bands. I also taught on the side. Young and old alike had trouble with the simultaneous coordination of hands and feet. The kids worked at it and most eventually got it. The adults....not so much. They tired of trying.
Eddie