Yes, they are still in other systems. As I understand it, the systems shown on the goid gal map only reference the powerplay/BGS components. There are still Thargoids in their classic systems, but they won't interdict you and don't have conflict zones. Note: hyperdiction will still happen ~20% of the time when jumping into a classic goid system.
Also, not sure if you got odyssey or which version you're playing (it split), but odyssey's foot exploration is where the money is in exploring. It can be a pain to find things, but there's bacterial colonies and fungal stuff you can scan and turn in for more than planets were ever worth