I don't understand what's wrong with writing something upbeat or aggressive in a Maj. key, matter of fact, I think it's more of a challenge. I guess most people like feeling bummed all the time.
Don't get me wrong, I love minor modes, but what I'm saying is diversify. It's like track 1 thru 10 are interchangeable. Most people have many different sides to their souls, so why just write about 1?