The reason why everyone doesn't do it is because it requires significant capital to be able to support a dev team through production for a number of years.
Not to mention they will still have to deal with publishers potentially fucking them over, as shown with the Helldivers 2 PSN fiasco.
Great insight it a number of civilisations that have collapsed throughout human history. Explains their rise, peak and of course collapse in great detail.
Arma 3?
Haven't played it personally, I'm not big on milsim games, but it's got a decent following. Might not have the accessibility options though.
I've heard good things about Battlebits, for what it's worth it seems decent.