Well to be fair, that doesn't mean it is impossible, only that it isn't as straightforward as one might think. Similar things were said about Classic WoW, and eventually, they did manage a way to do it.
With that said, the rumoris that the team behind the Crash remake is developing it, so if anything I would expect a full remake (most things developed from scratch in a new engine) and not a simple remaster (better textures/higher resolutions in the current D2 engine).