Epic can't make a dent because their product is dogshit.
Customers don't care that Valve takes a well earned cut (that only applies buying directly from Steam); they care that their games are on a platform that's actually fucking useful. If Epic didn't insult gamers shipping that piece of trash and had put work into actually providing a product that could possibly be considered acceptable, they might have been able to make a dent.
You're not going to take market share with shitty gimmicks if your actual product is a crime against humanity no one wants.