As mentioned, it was written by the mod author, and they're trying to explain that they're "not just charging for a mod" which is often a detraction leveled in cases like this.

(However, even if they were just literally charging for a mod, I'd be fine with it, Factorio has some of the best dollar for playtime money I've ever spent, maybe Minecraft and Dwarf Fortress come close).

Not "better", but for a different target audience. Also written by the author of said mod, who was hired to work on the expansion.