Personally, I think you took his comment the wrong way & it's actually one of the most accurate comments on here.

So you have some designs on paper, great! Show these designs to anyone, everyone & gauge their interest. Remember, what a user says is very different to what a user does. Just because they say they WOULD sign up for something, doesn't mean they WILL sign up for something. Friends, family (& professors) are likely to be biased out of love, widen your reach.

I wouldn't code anything until you have done the above. The PG quote is basically reaffirming that your idea is worthless right now. Millions of developers are out there with ideas. Thousands are even out there with an MVP. Get user feedback from day one & make sure you're idea is actually worth something (& remember that 90% of good ideas aren't).