I love Rise of Nations, but I have an issue with the claim that Rise of Nations is more flexible and has more options than Starcraft 2. It's true that when a race in Starcraft becomes weak and unsure of "the right way to play," that can cause a negative feedback loop. But I don't think that says much about the "depth" or "flexibility" of Starcraft vs. Rise of Nations. And this is because you're missing one crucial thing: the Starcraft 2 has a massive professional competitive scene, while Rise of Nations never has.
I know you guys have said you're not interested in the cut-throat, "figure out every nuance and build order" type of competitiveness, and I'm the same way for my own personal playing (although I love following the professional SC2 scene as a spectator). But you have to recognize that, if there was an extensive competitive scene for Rise of Nations, games would almost certainly look a lot different. Heck, in Starcraft, there can appear to be more depth and flexibility among casual, non-competitive players, just like for casual Rise of Nations players. But at the highest levels of competitive play, some of these "options" simply aren't viable, because the players no a lot more about how to read what their opponent is doing, and what their opponent's options are in the next 2-3 minutes of gameplay. If you decide to execute a clever strategy that involves sacrificing some military for a fast boom, but you haven't analyzed the timings correctly, a skillful opponent might realize that there's going to be a 30 second window where they can punish you and win the game. In a competitive game, there are fewer viable options, but I still think the strategy and tactics are deeper, because you need to know what options of viable and how to identify what your opponent is planning.
But just because casual opponents won't be able to punish suboptimal strategies, I don't think it's accurate to say that a casually played RTS truly has more options than a fiercely competitive one. I have no idea how to play chess, other than the rules of how the pieces move, so I might think that I have tons of options for how to move. Obviously, an even slightly competitive chess player would realize that only a tiny portion of the legal moves are even remotely viable. I certainly don't think that means that fiercely competitive chess is somehow shallower or less flexible than casual chess.