As for the whole childish thing though, SW is after all as much for children, technically more, than it is for adults.

Except I didn't care about that stuff when I was a child, and I was only interested in Luke's journey to the "creepy" Emperor :D

All in all the Empire, or rather a small squadron and by effect the Death Star II, being defeated on a forest planet by a few rebels and a primitive society kind of makes contextually sense. It's silly, but so is a farm boy saving the day with a single torpedo.

I'm not sure it's the same: even before becoming the "only hope" in TESB, Luke was strong in the Force (as Vader admitted himself), not an ordinary farm boy.

But all in all having the Empirical war machine defeat by someone technologically primitive kind of fits with the motifs of the trilogy.

I disagree. I know that's what Lucas said, but to me, it doesn't fit at all: why did a lot of people want a great epic final battle between the Rebels and the Empire? So to close the Rebellion's story-arc started with ANH. That's the actual motif of the whole trilogy: fighting to break free from the oppression. What we got instead was a bunch of floating Rebel starships standing-by for almost an hour until the ending scene. It was very disappointing for some.

Also the ANH rough draft literally had a bunch of Wookiees being taught how to pilot fighters within a single day and destroying the Death Star.
Now that's silly!

I can't find it in your link, but I'm glad it didn't make it into ANH :D