More and more, the NBA is getting away from "teaching" and they're expecting players to come in ready to play. If you're not ready, teaching will happen in the G-league. No different than other sports. In football I'm old enough to remember when quarterbacks weren't even expected to get on the field until at least 2-3 years of sitting on the sidelines. Now most quarterbacks who are high draft picks are expected to play either right out the gate or by half way into their rookie year.
NBA teams don't practice nearly as much during the season as they used to, so the old school mentality of teaching rookies is really fading away. Player are expected to do way more independently these days: hiring their own trainers, hiring their own skill development people, hiring their own dietitians, etc. Maybe Malone landed on the extreme end of that spectrum, but I think when today's players decide to join the league early they need to realize they're no longer going to be pampered and groomed like in the old days. NBA teams, especially if they're winning, simply don't have time for it.