Yeah but the classic team doesn't have the resources to remake a game from scratch. They couldn't even remaster War3 correctly.
Also that link headline is misleading. They recovered enough source code to have a game, how do you think they made patches and an expansion. The thing it sounds like they didn't recover is the 3D models used to generate the sprites and backgrounds in the game. Note that Starcraft Remastered didn't have those either, they touched up everything like pixel art, but that would get pretty challenging on Diablo II with it having so many more characters and animation frames at larger sizes, also many of them being complex "paper dolls" composed of interchangable parts.