Yikes. These game storefronts are not exactly rocket science, they are like primitive e-commerce sites. IIRC it took Apple and Google less than a year to slap their app stores together and I would certainly expect Epic to have spent very little time on theirs originally.
But I think whatever Epic does is futile anyway, even if they hired the best of HN and hand-crafted a feature-rich masterpiece of a storefront the simple lack of interoperable multiplayer, mods and DLC would still be a massive disadvantage.
Remarkably Steam has been successful as it is because Gabe Newell is the king and isn't accountable to shareholders and bean counters, much as Elon has been successful at developing reusable space flight. (Of course, there are counterexamples such as Mark Zuckerberg who keeps running Facebook into the ground but maybe there's a reason there is always a frown on his face.)