I think his FTs are a concern, and the associated reluctance to shoot late in games. As to the rest, 90% of his shots take place inside 10 feet, not in the restricted area, and that is to me a plus not a minus. If you don't shoot 3s you shouldn't take many if any shots outside the paint, there is no point. He's basically what would happen if instead of Giannis shooting 20% of his shots from 3 (and being really bad at it) he just went into the paint for all of those possessions. Are we worried about Zion's shot selection (he takes more of his shots inside 10 feet than even Simmons).
I think it's a product of people thinking... "PGs have to shoot", if you didn't know what position Ben played and I said... "Hey, here is a player who is 6'11" 240, passes like Jokic, Rebounds like Lebron, scores with the effiency of Gordon Hayward or Jaylen Brown, and is arguably the single best, most versatile 1-5 defender in the league, but he can't shoot outside of the paint and he hits only 60% of his FTs" you'd say... oh okay, so he's a top 5 PF in the league? Yes you have to build around him, you have to build around any player that isn't KD. If you have Lillard you know you need a lot of guys who can help his bad D, if you have Embiid you know you need shooters and someone to get him entry passes. If you have Ben Simmons you need stretch bigs and guards who can shoot.... but that's not different from what you need with Giannis, or LeBron (current), or any other guy who wants to use his size to get in the paint and score or kick but isn't a real 3 pt threat on his own.