Because in practice that "always-on DRM" is actually just purely an advantage for the customer with zero downsides. It only sounds like you're making a good point when you frame "provides the best shopping and library experience in gaming" in the least charitable way possible. The Valve hate-boner is so weird.
Can't you run old versions by setting the version in the game properties?
> always-on DRM is actually just purely an advantage for the consumer
Look me in the eyes and read this quote to me again. Then think about how yourself from 20 years ago would feel about reading this quote from someone else. You've gone so far down the rabbit hole but you don't realize you're in one.
There are disadvantages. e.g. if you don't want to update a program (maybe the new version breaks your modded setup), too bad. Or if you need Windows still for compatibility, it no longer supports Windows 7, so you have to go hunting for old versions of the client and fiddle with it to prevent updates (if that still even works), at which point you'd might as well just mod it to remove the DRM instead.
Basically, it creates a failure point for setups that should otherwise last and be stable several more decades.