This is the way.
Minds are already the primary movers and shakers of Culture society, they don't need to take over, the status quo has already been aligned with their interests. Minds are created by other Minds performing essentially mental eugenics, the desire to dominate others would be a dangerous trait for them to let slip into the population.
No single Mind has dictatorial authority over the Culture though. I could see an argument for it being oligarchal or even a caste society. But I'm not following your reasoning on the enlightened dictatorship part. Could you elaborate?
Who's the eternal benevolent dictator of the Culture?
It would certainly be more convenient if they/them became a generic pronoun for everyone regardless of gender. But at the moment it's not nessararily polite to use it that way in all circumstances. There are people that only use gendered pronouns to refer to themselves, to the exclusion of neutral pronouns like they/them. Generally if there's any uncertainty about someone else's preferred pronouns you can just ask. If you wanna skirt around it you can introduce yourself including your pronouns which will give others a safe opportunity to do the same. Messing up someones pronouns can be embarrassing but it's not the same as dropping a slur. (Though it can still be very hurtful to those involved.)
Remember kids, just say "neigh" to Premarin.
Eberron too please!