Steam has the stance that it will "release" a version where you just get valid license from the game you purchased and downloaded before they shutoff service should it belly up in the end. Epic does not really have the same thing announced anywhere, but I'd assume similar thing.(Note, Epic has more net worth than Valve, they can afford to shut EGS and still provide EOS/license check almost indefinitely even if they stopped selling games on EGS as a platform.) And it's why steam has that 3rd party DRM tag/block on games.(I wish EGS has this tag or information as well)

Denuvo is quite different however cause:

• it's harder to patch out, and the platform do not have access to those part.
• it adds additional game breaking point( say if you bought a game that has it and also "always online" you need game company, Denuvo, storefront platform and your internet up to play that game.)

I think steam and epic would have bot that buy and patch out the game's DRM like day 1 after release, they don't care cause majority of their user won't bother downloading shady program from a shady website. The publishers however care and thus we have this issue of them "trusting" Denuvo to shield them from piracy during launch window.

I still vote with wallet and generally only buy single player game after they removed Denuvo or just buy those on PSN, cause I trust platform to last longer than Denuvo.