I’m assuming you’ve played it, but for others reading this: It’s more than just bonus content, the base game has been reworked to integrate the planets into the progression.
A Space Age playthrough is different than a base game playthrough basically from the get go.
Yeah this is why I’ve never tried it. When I was still on reddit the way people talked about space age turned me off. It seemed like a massive time sink that was more about upping the logistics to the nth degree than about new mechanics.
I really like space age so far because of how differently I’ve had to play on the first planet I landed on.