I had issues with this as a kid too, and sometimes it just takes someone saying the right thing, and it'll just click.
I think it's often the result of the three point line. It's syren's call hits far too early for players, and kids wind up backing up to shoot it long before they're ready. And there's only one way to hit it at that point, and that's to flatten out the shot and let it rip. It becomes more of a throw than a shot, and it winds up affecting the shot everywhere else.
When I was a sophmore in HS, I had a coach tell me to "shoot it like I was in a phone boothe", and for whatever reason, that clicked with me. Certainly more than "get it up", "keep your elbow high", "get your legs under it", or whatever else gets thrown around. But what clicks with one person may not with another. Also, it may have been in part of just getting naturally stronger that year too.
One of the workouts I tell people here all the time is forearm curls. People do calf raises all the time because they help with quickness and jumping, but the truth is is that this is a game played at the extremities of the body. The stronger the forearms, the quicker and more elevated the shot becomes. It almost immediately improves rotation, range, and quickness of release. It also helps tremendously in ball handling, as the ball will snap better.