That’s the thing about basketball. There’s one ball and five players on the court at any given time, and multiple roles that need to be filled. A lot of guys can score but not every guy can rebound, defend, screen, do role player things, etc. So role players end up role players because they’re better at those things than their teammates and are probably just a little less efficient as scorers. On the flip side, a guy like Donovan Mitchell can probably be a really good defender if he didn’t need to focus on scoring but he’s often the best scorer on his team so he fills that role and his defence suffers as a result.
It’s all about roles.