>>299940575
What kind of worlds assets we talking?
I use cc0textures/texturehaven for PBR mats if available.
CGTrader/ModelHaven for generic models (CGTrader lets you filter by free/royalty free), although I usually end up having to modify them anyways due to either not being low-poly enough, or look too generic to start but 'good enough' for a base to build from.

Otherwise there's some asset packs on Unity's own Asset store which I grabbed a couple of for quick prototyping, but it's 100% placeholder stuff. Other than that I build shit myself like pic related.