If Epic makes no guarantees to the purchasers of content, I don’t see how anyone can justify using it. I don’t think anyone is asking that they verify each and every asset…just that some protections should be offered so that those purchasing Marketplace assets aren’t held liable when violations inevitably occur.
Other 3D marketplaces do already make some guaranteed protections against liability (e.g. see TurboSquid Can Now Indemnify 3D Stock Up To $1M - TurboSquid Blog).