After all, it's always fun to see big army fighting, and I'm pretty sure tons of people enjoy that. My son loves playing Totally Accurate Battle Simulator (I know it's not an RTS), but SC2 UI is just too complexe to begin with .
A new RTS should have a more progressive learning curve where ultra casual player would not have to create control group, micro anything, etc. And only when you reach a higher league, you start to micro because it gives you better army control. It does not have to be a different game, it could be implemented at the level of the UI.
I know some people are against that, because they think that people won't learn the "true" game. But casuals don't care about being grand master, micro, etc. they just want to have fun.