There's also examples of modder-made successes like Arsenal of Democracy and Darkest Hour (which was itself made by the team behind EvW). Besides, there's a big difference between signing me on as a contractor under Paradox management and just handing the IP over to me to make the whole game. Quite a few of the Paradox scripters were modders before they were hired, so technically HOI3 is a modder-made game to pretty much the same extent that me working on V3 would be. So are all V2's expansions, since both Wiz and Dark were modders before they signed up and both contributed to various parts.
Anyway, while modder-made games have a pretty bad hit rate which has gotten worse in recent years, it's not really that much worse than the general level of cancellations in the games industry. Until very recently, the majority of all computer games were cancelled before they were even announced, either killed off early in the design stages or else just not funded. Crowd sourcing has changed that, which is why proper, talented, fully-qualified professional games developers can release things like Godus without a publisher intervening to prevent it.