Assets were rarely used in the final build outside of set props and NPCs, since we did not have enough animators to hand-create the park population. Despite having an art department cranking out several dozen unique models, texturing them, and implementing them into the game we needed more minor props for set dressing. It takes a significant amount of time to produce a single asset, even with multiple artists, which is a lesson we hope other devs take away.
Using external assets is entirely fine, as long as you work hard to match the style.
