I remain a sucker for MDF terrain, and while I'm leaning towards pre-painted these days due to a lack of time, I was pleased to come across Mad Gaming Terrain at Salute this year.
They primarily seem to be aiming at the 40K market, but they had a modular system of "Hab Blocks" that would definitely suit Infinity.
There were plenty of different examples for how you could use them.
I quite liked the "abandoned and overgrown" look this example had. The sand and rock piles really help bring out that they've been abandoned a long while.
They can build up to quite large structures too.
Walls and crates remain a reliable option that looks good and has a narrative.
With some very small changes you can make a real ramshackle assortment of goods yards and workshops.
They also had a bundle deal to get the current standard "London Grand Tournament" terrain pack for 40K. If competitive 40K was your thing, this seems like a pretty good deal!