Way too early for me to evaluate ratings and stuff, but Zion's perimeter defense was atrocious from what I saw.
I think everyone is undervaluing Barrett's shooting. He can't shoot on-ball right now. His shooting off-ball is at least serviceable and has improved over the last year. He barely played off-ball in the games in Toronto. He's not a guy with a ton of handling/burst to be a primary creator anyways. He was not in his ideal role in these games, so I wouldn't be too critical of him yet. Only conclusion I would draw is that he has a way to go to be solid as your primary creator at the NBA level.
Here is the whole issue with RJ in a nutshell, if there is one. At least for me. There's not any one thing you can really point to with him that is at an elite level, even amongst his peers. Except maybe for more intangible things like "feel" and basketball IQ. His athleticism is good--he'll be a better than average athlete on the wing in the NBA, but not elite either in terms of getting up over his defender or, even more so, past him. His handle is okay, good enough if he's never the primary creator on the floor, but definitely not a strength at this point. Same with his shot, as you said. Great size for a guard but without great guard skills and just decent size for a small forward with good ability as an off-the-ball wing. One thing definitely going in his favor is his tremendously young age, though. He's young for his class, almost a year younger than his teammate/classmate Cam Reddish, for instance...
...but not as young as his other teammate/classmate, Zion, astoundingly (RJ turned 18 in June; Zion in July).
And Zion, having just turned 18 a month ago, would be one of the top 3 largest men in the entire NBA in terms of just sheer weight if he stepped onto the court TODAY. I saw you are a fan of Zion too so I'm not trying to convince you or anything, I'm just still so in awe at the size of the lad that I have to talk more about it.
Every year, there are athletic "freaks." But I always think of it as a relative thing, as in it's always compared to the rest of the class. Marvin Bagley, for instance, was this year's pure athlete, with explosiveness lauded as absolutely elite. But to me Bagley is a guy with explosiveness that's a strength for him, but not off the charts when compared to the other plus athletes at the position in the NBA. There are a lot of great athletes in the NBA, after all. But Zion... Zion is virtually unprecedented just in terms of the sheer physics of the kid. Beyond the NBA... just in terms of the mass and power and lift being generated.
Take Myles Garrett for comparison. An absolute freak in the NFL. Per his combine, at 21, he was 6'4, 272, with a 41" vert. Zion is a freshly 18 year old kid that just reported to Duke at 6'7, 285 pounds, and while I have not seen the actual vert measurement published, he reportedly broke the max vert record at Duke. The video shows that they actually had to put something under the rack to raise it up when he cleared it his first jump.
LeBron is the freakiest human I have ever seen in terms of his combination of size, strength, speed, explosiveness. Might be the freakiest ever in terms of the major pro sports. And Zion at 18 is way heavier, maybe an inch or so shorter, and I would argue more explosive than LeBron at the same age. I can't believe I can even make that claim with straight face.
Then add to that some relatively unique traits that Zion has already shown at his young age, some of which aren't even dependent upon being bigger or jumping higher than his competition. First and foremost is his ball handling, which actually looks really good. Not just like a "hey he can put the ball on the floor if he needs to" or "I've seen him go coast to coast" kind of good for a big, but actually good. He has a compact controlled dribble and, unlike so many uber athletes, looks like he may actually be able to utilize his explosive first step bringing the ball with him. He looks in control dribbling in transition even with contact and can even keep his eyes up a little while running the break, which a lot of bigger guys struggle with early on. He's a plus passer. He's also extraordinarily skilled at finishing with finesse and agility around the rim when he can't just go up and over the defense.
His jumper is really whack though. Currently looks like he's playing beer pong. And I'm conveniently ignoring his defense as much as he has thus far, just because the settings haven't been exactly defense rich environments, but I do doubt that will ever be his strength.
Nevertheless, this kid is just about the most intriguing and unique prospect I've ever seen and I can't wait to see what he becomes and I'm rooting against that being a bust.