Why unfixable ?
There was progress made during the second half of the regular season regarding Brown/Tatum/Smart moving the ball before traps arrived, better shot selection and with less forced dribbles. But they struggled at times in the playoffs, where defense is better and opponents adjust and throw different looks at a team. I got as frustrated as most when Jaylen would dribble into trouble, but because of the lack of off-ball movement and with the shot clock winding down, sometimes he had no choice but to try something to create a shot for himself or others. Tatum's struggles in the finals were sometimes due to the same reason - not enough options to go to.
The fixable part is up to the coaching staff. They have to put in offensive sets that include off-ball movement and off-ball screening and cutting. You think Golden State's players are just this naturally creative bunch who figured out their movement-heavy offense on their own ? They were taught and coached creativity within set offensive patterns. I would say that Curry, especially, does have a natural feel for where to move and how to cut to open up his shot opportunities, but that is not true of the entire team.
I think your last sentence really gets to the heart of the problem - Curry is the Warrior's best player, so the coaching staff is going to build offensive sets that cater to his strengths (I also think you're underrating Klay Thompson's movement, but that's neither here nor there). You can give our guys the most free-flowing sets in the world, but our best players are not naturally great at sharing - or moving without - the ball.
When I say I don't think it's fixable, I don't mean they can't get better at it.
It's got two parts:
1 - I don't think it's ever a style of play that will come to them as naturally as, say, a Parker/Ginobili/Duncan Spurs, let alone the gold standard for this (the 2002 Kings). But I also don't think it's a coincidence that after Derrick White (TGF) came over from San Antonio that the team started playing better.
2 - I don't think the regression to standing around is going to stop against more difficult competition and when the shots aren't falling. Game 5 was a pretty good example of that: running down the shot clock in the half court & bad spacing leading to pretty ugly basketball - this is something that I think Jalen, TGF, and even Williams mentioned after the fact.
All of these guys are All-World talents. But even when things are clicking I'm reminded much more of the Heatles or our Big Three when Rondo was on the bench, the
your turn, my turn offense*. And, hey, both of those teams won championships, so it's not a bad thing. It's just
a thing, hopefully it's just an aesthetic problem on my part
