Games need to be short. Games need to be fast and have continuous action. Buildup phases need not apply. Rushes need to be viable. Unit counts need to be restricted. Attack uber alles--defense need not apply.
A game design article recently had a good word for it: homeostasis.
Twitch-friendly games are ferociously anti-homeostatic. They want balance to be metastable--easily knocked off and then the imbalance snowballs to defeat.
Supreme Commander, on the other hand, is practically the anti-Twitch. It is strongly homeostatic. If you rush an opponent on a large map, your L1 units are running into L2 defenses. If you don't knock your opponent out, there is now a LOT of quickly harvested scrap metal sitting really close to his base and really far from yours. Defenses are strong and problematic. Unit counts are large.
Yes, i agree.
But besides that, also the planetary maps where an awesome idea, but for me is just very bad in practice. Also performance was problematic from the first launch. Though improved a lot, still not where i'd like it to be. (though BAR also still has a road ahead, but we're close to updating to new GL rendering, which can improve unit-rendering multiple times over... :) )
I think the problem was that they worried too much about making it Twitch-friendly and forgot to, you know, create a fun game.