The first is that I don’t understand how this doesn’t also apply to Steam or Epic Games or any other basic storefront (except GOG of course).

There were three points in the post you're replying to. Not all Steam games have DRM; I'm going to assume we're talking only about games using the their DRM:

1. DRM server shutting off -> Steam has been around for a long time, longer than Denuvo. Steam makes a lot more money than Denuvo. Steam is not as publicly hated as Denuvo. Because of these things, I don't think Steam will be shutting down any time soon; Denuvo shutting down is a much larger concern, especially due to public perception. Here's a decent answer to the question anyways: https://gaming.stackexchange.com/questions/255424/what-will-happen-to-my-owned-games-if-steam-were-to-close .

TL;DR 1: It's not as much of a concern for Steam as it is for Denuvo.

2. Game company shuts off and is unable to pay DRM subscription -> This depends on the license agreement between the DRM provider and the company. The comment you're replying to implies that Denuvo has a subscription fee for its use in a product, and I'm going to proceed under this assumption. I doubt Steam requires any form of subscription fee to keep the DRM working - I would expect that, as they are a storefront, they pay for that via a percentage of game sales. Denuvo isn't a storefront, so I would expect if they have a subscription fee then this would be a Denuvo concern that doesn't apply to Steam.

TL;DR 2: Steam is a storefront, and it's expected that their sales percentage would cover DRM costs for the game. This is a concern for Denuvo, but not really one for Steam.

3. Internet going off -> Steam has a well-known offline feature that works reasonably well. Companies that use the Stream DRM system are using libraries intended to work with this feature - that's not to say they can't purposefully make it unplayable offline, but it's generally well-done. The problem is that it requires you to enable offline mode before your Internet goes out. This is something that's regularly complained about, so I don't think your "[...] I don’t understand how this doesn’t also apply to Steam [...]" statement applies.

TL;DR 3: Steam DRM is regularly complained about in this regard.

I dislike Epic , so I'm not the person to give them a reasonable defense/discussion - you'll have to find someone else for that.