It's fine if they don't care that they're playing sub-optimally. That doesn't mean that giving the players the choice between insane micro and playing sub-optimally is good gameplay design. Any given game should (and usually is) designed around the idea that players will apply themselves and try to win to the best of their ability. If people like micro, that's absolutely fine! But "micro is optional because you can always choose to play poorly" is not.
We can apply this school of thought to other genres to see how poorly it holds up. Learning combos in a fighting game might be hard and people might not like it, but you would never say "you don't need to learn combos, because you can always just choose to lose". Of course it's fine if people want to play that way, but telling people that micro is optional because they can choose not to be competitive is not true. It's only optional in the sense that you can decide not to engage with it at the cost of not playing the game well.
I would agree if we were talking primarily about multiplayer. It absolutely applies to some of the most hardcore games. However, the beauty of nearly all 4x games is the option to do what you want and see what happens, same with RPGs.
If the game was aiming for us to play optimally, then everyone would just chose the same traits, civics all the time, and have cookie cutter builds. That's no fun.
I certainly don't feel like I'm missing out, or like I'm left behind by being a bit more relaxed with the game.