Lucas may have had some collaboration, but I would suspect he felt less need to follow what others advised than he would have in the old days.

The weakness of the prequels is not a lack of story. There was plenty material to make story from. The weakness is that the mentality and spirit of them is screwed up to the point of pushing artificiality and lack of depth and lack of emotional resonance. This affects everything, from the visual look, to the story, to the acting. A total break with how Anakin was originally envisioned in the OT didn't help either. Nor did the inclusion of cartoon characters into a fictional universe that was established as trying to be more believable than that.

Of course the biggest amount of collaboration was visually and through the art department, or sound recording department. He also had a lot with the pre visualization whether as sketches, paintings or computer drawn.

I think this was going to be the case no matter what. I don't think it means he wasn't independent and unopposed in what he did in the prequels.

So what if he got some advice from friends, he didn't have to follow it. I think he went more unopposed when making the prequels. And whatever about intentions, he didn't get Ron Howard to direct TPM. As for the Carrie Fisher rumor, never heard that before, but we don't know how much she contributed and whether what she contributed was kept. The insipid TPM doesn't strike me as much her style.

I think on the prequels Lucas was more the dominant boss than he was on the OT -at least that's the impression I've gotten from what I've read. And hasn't he claimed to be 100% satisfied with the prequels? That's a big difference from saying he's 40% (or whatever he said) satisfied with the original films. That certainly sounds like he got his way more on the prequels, with less interference from other people.