Where did I say that shooting only mid-range jumpers is preferred?
Diallo is not great from the perimeter, but he's enough of a threat that defenders have to come out. Would I love it if he were a 6'6 point guard who shoots 45% from the 3pt line, can attack the lane to dunk on defenders, and who shoots 90% from the FT line?? Absolutely.
My point is that being a 1 trick pony in the lane is easier to defend. For a offensive player getting in the paint, if you are a threat to BOTH attack the rim (which I think Diallo is good at) AND pull up for a floater from 3-5 feet away, you are more difficult to defend. A dunk/layup is better percentage, but if you have additional tools like a floater, defenders/shot blockers have to respect a hesitation in the lane for the floater, and it can open up more layups.
Hope that clears up the point I was trying to make... it wasn't about knocking the idea of attacking the rim being the best option, but moreso a good floater creating more opportunities for layups or dunks.