Assets, and saying that is a very general term. I would say finding animations would be one of the harder things to find.
With CGTrader and TurboSquid, assets are “a dime a dozen”. You can literally find anything and everything you would ever want.
Finding animations specific to your project is one of the harder things. Unless you are making a fantasy casting game, then you have everything you need! For some reason, asset designers seem to think “if it aint blowed up lookin’ or mage castin’ it aint no good!” …
Anyways, finding reliable people is hard. I lost over a years worth of content and, money, from paying a programmer that used several other games code (he was contracted to other games as well) into my company project as well as just pulling in free content and charging me for “the work done”. I had some MMORPG thats unannounced, so, i have no idea whos game it was, and kite demo stuff all in my code. Anyways, finding ppl that are worth their salt is, at times, harder then finding the assets required.