It might make Valve unlikely to make another game and a lot of people, including myself, would be hugely disappointed but I don’t think it would have any major negative effects beyond those two.
Denuvo doesn’t make it impossible, it just makes it take longer, dependant on the interest of the crackers. The main need to be online comes from the initial Denuvo validation and for the ability to use others’ pawns. Being offline means you’ll just have to use generated pawns.
I think the concern some people have is that it’s a slippery slope. Sure, right now it might not be too egregious, but if this behaviour is just accepted, publishers will want SP games to be designed around mtx. There’s no limit to greedy peoples’ imaginations when it comes to squeezing people for their money, so god knows how they’ll limit your ability to play games without putting in either a lot of time, effort or money.