It's not exactly necessary to have FTL to reach post-scarcity for us (albeit maybe for a short period of time) as our solar system has shittons of resources already, we just need to industrialize them. But yeah, if you wanted a self-sustaining utopia on Earth (-ish, because the Sun will fry it all in about 150 million years if not faster unless something's done about it, which will require space industry anyway), we'd essentially have to return to peasant lifestyles where about 90% of the people grow their own food (compared to about 10% today).