Jackson was the director. The director is the boss. The credit and the blame.

A director of his reputation, on that *specific* franchise, is forced into nothing.

Del Toro left because of the excessive delays, he was not forced out. He had other immediate projects waiting to start.

Jackson advocated the 3 film change from 2.

Most of the weaknesses I address with The Hobbit films are not something editing can fix. They're more along the lines of over reliance on CGI and the resulting loss of suspension of disbelief.

Compare two escapes from Goblins from caves:

Escape from Goblintown:
https://www.youtube.com/watch?v=tE8KPmBYRrA

Battle of Balin's Tomb:
https://www.youtube.com/watch?v=kyevhryWKHk

And getting surrounded:
https://www.youtube.com/watch?v=aAtkiolzTFQ

Just the art direction alone on that last clip from Fellowship where they're surrounded by the goblins, compared with the CGI goblins in The Hobbit films. Editing is irrelevant. That is a decision that Jackson purposefully made to move away from prosthetic and embrace CGI, which hits at the core of what I was trying to convey in the OP.