When Phoenix Point went Epic Exclusive, I found this amazing Google Spreadsheet that honestly compared the features of Steam, Epic Game Store, and Piracy. I can't find the link for the life of me. Here's a comparison of all the game stores, sans Piracy. It's not really that good, because for some reason the person who made it considers "Trade Cards" to be a noteworthy feature, but it's enough to impress upon the point I want to make:
To the point, Steam hasn't "killed Piracy". Nothing can. We still have Somali pirates when Blackhawks exist. What Steam did was compete with Piracy. With their feature set, they successfully competed against a platform where consumers can get their games for free. Anecdotally, I've heard countless stories of people buying games during Steam Sales they would've never considered buying otherwise. Further stories of Steam Libraries full of bought games that the owner will never play. That's money and game exposure to devs they would've never had otherwise.
Now back to Epic Game Store... Steam has been directly competing with Discord for years now, because Discord is currently the #1 Gaming Social Platform, and Valve wants to have the best Game Platform period. Steam has an effective monopoly, but they're still innovating far and above what their competition is doing. But because EGS is a barebones game store, because they couldn't attract Devs with their 18% cut alone, because they had to resort to exclusivity deals, Steam has largely ignored them. If Epic had a killer store, offered rich features, played it fair, and brought in Devs through merit, you're god damn right you'd see Steam changing to adopt what works. But Epic f**ked this up. That adoption could've been a lower cut.
Truth is no amount of "Steam doesn't need 30%" arguing on forums will change anything. Competition will. Mass social protest can also change that, but you'd have a hard time convincing a large enough body of Steam consumers that "30% is really that bad" when you can't even convince most of this thread that. Competition is the easiest way to drive this kind of change.