He got by on his freak size and athletic ability at dook. He isn't terribly skilled and he isn't a great shooter. When he gets to the NBA he will find out that everyone is long and athletic. He will be good but he will not be a hall of fame caliber player.
This is why RR is known as the pinnacle of basketball insight. Everyone is long and athletic in the NBA? Damn, who knew? Everyone. Literally everyone. And yet still people who are paid to analyze these things are universally in agreement that Zion is (i) a top tier athlete even by NBA standards and (ii) one of best prospects to come out in this century.
He is a freak athlete but I'm not convinced how skilled he is at the game of basketball. So much of what I've seen him do is the direct result of being a much bigger and better athlete than his opponent. I don't think he has that advantage in the NBA. He definitely needs to improve his handle and his shooting range. He will NOT get every call and be allowed to steamroll over defenders like he did in college. If he develops and stays healthy, he could be a solid pro, like Blake Griffin (who was better entering the league than Zion, imo). If he doesn't continue to develop and/or can't stay healthy, he could have a pretty forgettable career.
I don't think anyone that matters believes that Blake was better entering the league than Zion. Zion was better almost across the board (although for Blake many stats are unavailable, like rebound rate), and he did it at a younger age and with less experience in the college game. That younger age part means a lot to projections; Pelton and others have found that certain traits players have as freshmen are more predictive than year to year jumps in skill/output.
Also in what world is Blake Griffin a "solid pro?" Despite facing a rash of injuries, he's finished 3rd in MVP voting (deservedly) and is a 4x All-NBA at the most stacked position (LeBron, Durant, etc...). He's got a really good shot at the HOF if he can stay healthy. A solid pro is someone like Kyle Korver.
I would guess he will be on a tier between Jimmy Butler and Lebron. That’s a pretty wide gap.
Seriously, that's a huge gulf. One of the best 5 players of all time, or a guy who tops out at third team All-NBA. I think that (barring injury, of course) Zion will be an MVP candidate in several years, and All-NBA worthy for most of a decade.