The game is about nuance and split timing. I ultimately look at how intelligently a player moves, how quickly they react and make decisions, how fast their hands and feet are. How do they handle the ball, how do they use subtle hesitations, how do they change speeds in a single sequence, how do they create shots for themselves, how refined and nuanced is their timing, how deft their shooting release is. These are things you can't ultimately teach.
Ben Simmons is elite in many of these respects. His ability to handle the ball on the floor, know when and how to drive, finish in multiple ways at the rim, etc. are already as advanced or even more advanced than the modern-day Blake Griffin who has learned to be an effective player away from the rim. The minute Simmons gets a reliable jump shot (assuming he ever does), he's already more dynamic than Blake Griffin and hence a top 15 player in the league.
Thon's movements are rudimentary. His handspeed and footspeed are good for a 7-foot player, but I wouldn't call them elite. He has to gather himself to be explosive. He's strong enough, but needs to add core and base strength. He can dribble, but can't really change directions with his dribble. He has good court vision and can make basic passes, but they aren't super timed. He can hit open jumpers with his feet set if he's given space, but he's doesn't look like he's going to hang over defenders and hit tough jumpers. His skill level is similar to Derrick Favors a year or two after Derrick was in the league. So take Derrick Favors, make him 2 inches taller, keep his weight down in the 235 lbs range to help his mobility, make him a slightly more confident ball handler and passer, give him a couple quicker post moves, and you've got what Maker should become. Not an All Star, but top 30 - 40 in the league. To be able to draft that at 12 is a coup--as much as being able to draft Andre Drummond at #9 or Andrew Bynum at #10. Plus he might hit 70% of his FTs.