THere is nothing wrong with Saric, period.
European players need a year to adjust to a longer 3 point shot plus some different rules concerning traveling.
And the game is faster and more physical.
Saric is making the progress you'd like to see from a top prospect.
He's played SF, PF and even C at times.
The outside shot could use some refinement (a little flat) but that's tweaking, not a fundamental do over.
He's physical for his size, tough as nails, and mentally tough as well.
And he's starting to show the great court vision he was lauded for in Europe, and that should improve as he gets comfortable with the NBA game.
He's going to be the starting PF for a long time, I expect him to come back next year stronger, with his shot refined, and a much better feel for the NBA game.
Comparing him to one and dones is apples and oranges, compare him to someone like McDermott, who was drafted in a similar spot, Saric as a rookie is already way above McDermott as a player.