It is pretty difficult being a 3 point specialist if you are not shooting with the correct form and technique plus the fact that the further the shot is taken away from the edge of the basket the further to retrieve it and the longer between shot taken and the longer it takes to become a good shooter unless you have a spare six hours.
Good team defence is five players guarding the ball, not five separate one-on-ones. The shell drill is where that starts, so here is how to teach help-side positioning and rotations from the first week of the season.
Rebounding is the least glamorous thing in basketball and one of the most decisive. It is also almost entirely a habit, which means it is entirely coachable.
Good spacing is only the start. The best modern offences teach players to attack the defence's rotations and play in a permanent 4-on-3 - here is how to coach that read.