From the perspective of a customer sales numbers are irrelevant for the most part.

Its useful in the sense of "can I expect a lot of people online" if it has multiplayer or, as you said, a vague use in "is there a chance of a sequel?" But that's the literal only use it has for you as the consumer.

Also this plague unfortunately effects more than just the Left. Most video game forums of any type get way too obsessive about these numbers, treating them as some sort of gospel about the quality and value of the game.

The Concord thing I 100% believe was them being more upset that "the Chuds won" than any actual care about the game. They weren't ever going to play it, but its failure is a huge blow to their control of the industry and convincing companies to make games Woker.