You're right - there's a lot out there already. While I usually wind up recording something for each thing I work on, most of my sound sources do come from sound libraries (such as those from "Hiss and a Roar" or "The Recordist", for example). But it's still just elements (a whoosh, an impact, a fire element, a low hit) all put together. Rarely is there a single sound in a library (like fireball_attack_01) that magically works perfectly in the context of the game I'm working on - editing and layering are always needed to get it right. Sound libraries just save me the time of recording the elements myself. And in some cases I need things I simply wouldn't record myself, like exotic animals, big drums, trees falling, explosions, etc.
Yeah, dragging a bag for wind is a funny thing - the idea is it's an easy way to get a generic noisy wind sound that could be used in any context and looped endlessly. Whereas if you recorded "real wind" you might actually be recording materials being moved by the wind, like fabric flapping or leaves rustling or sand/debris blowing past. Those things are cool, they just could only be used for specific settings.
That is a very interesting idea with having a day->night transition sound, thanks for sharing it! I'll talk about it with the team.
I'm glad you dig the random creature noises - I also wish they changed when you got closer. Ultimately I would like to accomplish this by adding vocalizations to the creatures' fidget animations, which are the short animations that occasionally play while they are patrolling around. Then you would hear the vague distant sounds from far away, the close-up fidget sounds as you get closer (which would match the animations), and then you'd start fighting them and hear their fighting vocalizations. However I can, I would like to support the immersion without getting too repetitive/annoying. Thanks again for sharing