Despite the harsh tone, I agree with him. He didn't say "make your own game, instead of complaining", he said "make your own game and see how much time it really takes".
That's exactly what I said before the update. It's totally normal to think it shouldn't take much time. Like you said, Renpy is very accessible. But in reality, everything always takes a lot of time when you crawl through the code. And it seems you can only really feel it by experiencing it.
For the sake of science, I measured the time I spent on this update. It took me around 7 hours, and some time more after the release. And during this time, I didn't even have time to carefully read the dialogs... It takes time.
But maybe I'm the slowest guy in the world, and maybe those "couple hours" guys should apply to L&P