If you're a nerd, you'll find these video series fascinating.

From SF Debris:
Hero's Journey and
Shadow's Journey

Notes:
I've linked to SF Debris videos in the past (example here) but always with caveats.
SF Debris's corny sense of humor is so cringe worthy that it was hard to seriously recommend his videos.
And yet, I still watched them.  They were short, they were punchy, and they catered perfectly to my ruined attention span.  After all, in this day and age of youtube videos, who has the patience to sit through a 50 minute episode of Star Trek anymore?  It was much better to just watch SF Debris's 10 minute summary, even if you did have to put up with his awful jokes.

However, as the above links make clear, once SF Debris drops his corny attempts at humor, and just embraces his role as a nerd documentarian, he really steps into his own.  He's created some fascinating documentaries on his website (and thankfully he seems to be dropping his forced attempts at humor).

Hero's Journey documents the making of the original Star Wars.
Shadow's Journey documents the making of The Empire Strikes Back and Return of the Jedi.

Both of these documentaries perfectly answer many of the questions that I've been wondering about - on this blog - for the past few years.
Namely, how was it that the same George Lucas was simultaneously so brilliant, and so awful?
If George Lucas was so awful on the prequel trilogy, then how did he create such a masterpiece in the original Star Wars?
And, if saving Star Wars was simply a matter of removing George Lucas, and getting the professionals back on board, then how come no one was able to duplicate the success of the original Star Wars? (You remember during the early 1980s every movie studio was trying to come up with their own version of Star Wars, but nobody could duplicate the success.)

The answer to these questions, it turns out, is long and complicated.  (Like, several hours long if you watch all the videos in SF Debris's series.)
But the short answer appears to be that genius story telling is difficult to duplicate.
It was a minor miracle that Star Wars got made at all.
It was an even greater miracle that The Empire Strikes Back turned out to be as great as it was.  (Watch all the videos for all the behind the scenes documentation.)

It was too much to expect that this kind of lightening-in-a-bottle could be captured 3 times.

People like to complain that there are only really 2 good Star Wars in the whole series.  But perhaps this is viewing the glass as half empty.
Instead, we should be amazed that George Lucas and his team managed to pull off not one, but 2 brilliant movies.
The fact that they ran out of steam eventually was perhaps inevitable.

Perhaps the problem is with us, the entitled fan, and the entitlement fan culture.  We expect that everything we get served has to be absolutely brilliant.  But the truth is that pure genius story telling only strikes rarely.  We got two absolutely brilliant movies, we should be content with that.

If Disney keeps churning out more and more Star Wars movies, the law of averages dictates that eventually they'll probably stumble upon genius again.  But in between the genius movies, there are going to be a lot of mediocre movies.  And we fans need to just accept that.  We can't have every movie be genius.