Your argument still is based on a fallacy. Even assuming all successful board game designers were good at game design (which is disputable), you can't deduce that all people who are not successful board game designers were not. That's like saying: All birds lay eggs, so if something is not a bird, it can't lay eggs. Sorry, fish, platypus and lizard.
So you say, no, i didn't deduce that, i never said that. But well, you made a statement about all fans, at least all fans of dominion, and implied they can not posssibly compete. Obviously you don't know every Dominion fan personally, so the only way you could justify a statement about all of them would be by forcing a logical conclusion. And your "logic" is, they aren't board game designers, they know nothing about boardgames. Your logical conclusion isn't there. Instead you serve us a bundle of anecdotes, unsupported claims, observations that lack a test group (So you played games by published designers and now think you can talk about games by unpublished designers?), and of course, the belief that everyone will do all the jobs he's good at throughout his live, because humans have unlimited time and never have to choose which path to go.
And all of that for what? To defend a fan card? Boy, they are not worth it. I have made plenty of bad fan cards, and if people pointed out why they were bad, of course i struggled to improve them, but sooner or later you have to see it how it is and, if there's no solution, let go. Unless of course you think that you don't have to try to make them as good as possible. In that case, you shouldn't be surprised if they turn out as bad as you predicted, though.