The launcher itself ran poorly compared to Steam's. I've had instances of it freezing performance down just downloading 1 game through Epic's launcher.
You've locked down games behind multi-year exclusives, pissing off many people along the way that we're now just seeing their Steam releases.
You've spent years giving free games away, promising not to do anymore, going back to doing it again.
The launcher and storefront are incredibly barebones compared to Steam's. In fact, any launcher not Steam, has incredibly minimal to go with other than just running games through them.