To be honest, I just try to do stuff that I think sounds cool, and I don't really consider accessibility. I'm aware that the kind of thing I do doesn't have mass appeal anyway, and I'm okay with that. By the same token though, I won't throw out an idea just because it's "too normal" or anything, and I'm not afraid to use variations of common progressions. As you say, there's a reason these things became common. :)

I also definitely agree that Classical etc. make great places to look for inspiration.