The problem is OBVIOUSLY that it tethers you to servers or some such application somewhere that needs to validate your game. And it could (and will) be turned off at some point. So the game is CLEARLY not yours.
We can run games from the 90s and 2000s, because there is no need for servers.
What's important to me, and to most gamers, is whether I can play a game for the duration of time that I desire to do so. So when I'm looking at D2 resurrected, I'm thinking something like this:
"If I buy this game, the longest I'd probably play it for is about a year. In future years I may return to it for briefer and briefer windows, asymptotically decreasing toward zero minutes per year as time approaches infinity. I think it's likely that Blizzard will keep the servers running for at least 20 years based on past performance. What is the area under the curve outside of twenty years proportional to the total value I intend to extract from the game?"
For me, I estimate the area at around 0. Even if I thought that a tenth of my total playtime would occur outside the initial 20 year window (extremely unlikely and generous estimate -- probably nobody exists like this), what is the present value of that future enjoyment? At a 4% discount rate and a fifty dollar initial purchase, the present value is $3. There's just not enough there for most people to be bothered about.
I've recently started playing Morrowind again. I was pleasantly surprised to see a healthy modding community that's still adding lots of new content, fixing bugs, and improving graphics. The UI is still clunky, but better than it used to be (with these mods), and the story is still one of the best games ever. It came out in 2002.
I would argue that many gamers are wrong if they think they're never going to want to revisit one of their favorite games. In fact the primary market for D2: Resurrected seems to be gamers who want to revisit one of their favorite games from 20 years ago.
We can run games from the 90s and 2000s, because there is no need for servers.