As far as I am concerned it's a post dedicated to piss the audience on which he used to promote it. Thus creating debate. Nothing more, nothing less.

But I think you strike on the point that big problems are relative. To me a huge problem is the lack of tech scene in my new area I've moved to, yet only a few hours away is a bustling one. But to most people that's a tiny problem.

If you're talking about ones that affect everyone, there are at least a few startups that I can name off by head (though mostly stealth) that are tackling big problems. It's quite an over-arching statement to suggest he knows every startup's mission.