I disagree with this. There are very very few players who can't benefit from college ball. LeBron being the epitome of that example. College gives you a base to build off of when you go to the NBA. It's a segway into a lifestyle most 18 and 19 year olds aren't ready for whether it be to gain weight before being thrown to grown men in the paint, or how to handle a team of equally talented players before being expected to lead a group of veterans as a teenager.
Take Davis and KAT for example. KAT was a face up 7 footer coming in and Cal stuck his butt in the post and turned him into the most dominating post man under the age of 20 in the country. He could have learned to play in the NBA, absolutely, but the transitioning helped from college to NBA as opposed to jumping straight in. Same thing with Davis. I remember watching Davis go up against Jones a few months before the season started and Jones made Davis his whipping boy for the 2 days we were allowed to watch. He was too skinny and didn't know how to handle someone so big and powerful (who's considered average when compared to NBA big men). By the halfway mark of the year, Davis had added weight AND adjusted his play to account for his body and the bodies of other big men and the transition helped him when he got to the NBA. The talent and potential were never in question. But even after a year in college, Davis' body still is having a hard time adjusting to the NBA with his plethora of minor injuries that can sometimes be related to his body. Imagine if he'd gone straight to the NBA at 180 pounds instead of getting up to 220 by the NBA draft the following year.
Point is, Bagley is incredibly talented but the things he's doing now at the high school level won't happen against the elite big men of the NBA. 2 of which I just talked about. He'd have a hard time, as an 18 year old, succeeding against Cousins, Davis, KAT, Embiid, etc etc. I still think he'd look better at the same point in his career if he had 1 year of college under his belt at a program like UK.
/rant
