I'm pretty sure he means that by being a critic on the sideline, you have a better chance of being right, but you have much worse odds of doing something great. Or said differently, if you never try, you never fail, but you also never succeed. I don't think that's an inappropriate response to someone who's saying "3/4 of these ideas suck".

And no, what the person he's responding to is saying aren't objective truths.