For me, its their utter disdain for Linux, my primary gaming platform. Their client doesn't support Linux, games that have Linux builds on Steam or GOG don't on EGS, they refuse to make Fortnite compatible with Proton (Windows compatibility layer) despite saying how easy it is to support Linux with their anticheat, and public statements by the CEO about how they hate Linux.

I also don't like the exclusivity agreements, even if the initial exclusivity window doesn't affect me. I bought Rocket League on Steam, and now I can't play it there anymore (online at least) because they made it EGS exclusive. I could've asked for a refund, but I got my value from it and got it in a bundle anyway (was technically "free" with purchase of the Steam controller/Link), but it still rubbed me the wrong way.

Steam actively supports my platform, and GOG makes Linux builds available (and even provides Linux-native packages for old DOS games). Why would I give EGS any of my money? I'll claim their free games and play on Heroic as long as that works, but I'm not going any further than that.