For argument's sake, if you were to remove Lonzo's first summer league game from existence, he shot 43% from the field. Not great, but not awful. I think the nerves/pressure was too much for him in that first game b/c of the hype machine.
He looked more comfortable on the court in all his other games, including the game he shot 6 for 20. While his shooting is somewhat of an issue, it's his on-ball defense that should concern Laker fans.
I would be pleased if he can shoot 43% during the regular season. Jason Kidd only did that one season his entire career -- his first four years, he shot 39%, 38%, 40%, and 37%.