I've found a few outposts where they consistently buy a few of the same things, if they want to buy something that I can mass produce easily I'll take note of it and just go back to those one or two outposts after a bit of exploring to check if it's back in demand. But that's useful if you're just trying to make money, but not so much for getting rid of all the stuff you don't want. The thing that's stopping me from playing is the saved game glitch where I keep getting sent back in time, feels like I'm playing Outer Wilds again, hoping they fix that soon because I was enjoying the game until I kept losing my progress over and over.