Here's where I think the misunderstanding is, and maybe I should have made this point in my original comment: I do think there can absolutely be cases where a dual license of GPL / commercial can make a ton of sense. I think those cases tend to be for projects like Linux, Blender, etc.
But what I'm saying I personally think is a bummer is that for years, most open source projects - down to even small but useful libraries - were put under GPL simply because it was "the thing to do".
Like Carmack says, in my mind that is a net negative, since these libraries then were not able to be used by projects which were under other licenses, due to their copy-left viral nature.
We don't know how many projects would never have been written at all without GPL as a license option. Making it difficult to determine whether it's a net negative or not.
