Why would anyone at Blizzard think it was a good idea to do anything with D2 while they have D4 underway? Even if it was possible? (It's not).'Hey, I know we're spending a lot of time and money on making the best D4 we can, but let's simultaneously distract ourselves and the fans from that work and siphon away some of our customer base for D4 by releasing a remastered D2!" "Genius! Here's a huge bonus for you!" Come on, it's like Apple working on the Iphone 12, but there's a hardcore group who just loved and old phone made by another manufacturer, so they're going to rehash a version of it just for them. Not gonna happen.
It could be argued that it's important to look at their products in terms of IPs and not individual installations. For instance, the Warcraft IP making money off a WoW expansion, WC3R (lol), a movie, microtransactions, swag/toys, etc., is all a win. All of it represents either an increase or a continuation of maintaining capital for them as a company.
Investors may or may not see it that way. They might want an individual thing to excel as well as it possibly can. But in the long term, I think this is also something that is considered at quarterly calls because it's more indicative of longterm success. Box sales are just a blip on the radar--if you base all your success on them, you'll just be chasing temporary highs.
This is why I argue BlizzCon and maintaining Blizzard IPs as a lifetime fan/family identity is more important than just selling the next big thing.
Another thing could be argued--I don't think a D2 remaster would ever have the staying power to upset the multi-million dollar box sales of a major new installment. If Blizzard did it, much like the SC remaster, it would probably be either a labor of love or just for existing fans. I don't think any of their remasters have turned huge quarterly profits on the scale of a major release.