I think the argument being made is that because Warcraft is a long running and ever evolving franchise, there’s not one single work that’s always going to stand as “perfect uncontradicted canon” forever.
The franchise has always operated in such a way that every new game, expansion, novel, comic, etc, elements of the previous entries are contradicted/retconned. Warcraft 1 might as well take place in a different universe than Warcraft 3 or the Warcraft movie. Indeed, it largely does.
So if the idea that future retcons renders this book without any value, then the same can be argued of the Shadowlands expansion, as it’s inevitable that elements of that expansion are going to be contradicted/retconned in future material as well.
But we don’t just play an expansion because of how many/few retcons it has. Or how likely it is/isn’t to be retconned in the future. Similarly, many people buy these books because they enjoy the art, stories, the world building, or collecting of the book in and of itself.
Classic/Vanilla’s been retconned to heck and back, and people still go back to it. And many are looking forward to Burning Crusade, which I’m pretty sure features more retcons (and major ones) per capita than any WoW expansion before or since.