Here is another take on Kuminga -
link. This one is more balanced than the podcast I shared and acknowledges his physical gifts but still highlights his flaws.
I'm not pretending to know how he will pan out. He could develop into a great player. He has the tools and in the right system that could work. But the limitations identified should at least question his standing as the fifth best prospect.
From what you've written, you seem to be explicitly relying on what others are saying without giving your own impressions, which leads me to believe you may not have had an opportunity to see Kuminga in game film. I managed to watch about 10 of his full games with the Ignite and I came away with a different impression than some of his detractors that you've read. He certainly has his flaws, but I think some are overemphasizing his flaws and giving the impression that they're not fixable.
In my opinion, his flaws are:
1) Jump shot. He's not reliable outside 15-18 feet right now. But on the bright side, his form is very nice and he shoots with confidence. He goes up without any hesitation and believes he's going to hit every jumper. With his form, repetition should make him into an acceptable shooter (say .330-.350 from three).
2) Team defense. Frankly, I'm not sure that the Ignite team had any extensive defensive schemes. But Kuminga seemed to have trouble working defensively with his teammates. Now, that's probably to be expected because none of them had ever played together, so I can really list this as an incomplete rather than a bad grade. On the bright side, he was an engaged defender, he didn't take plays off on the defensive end, and as a man defender or when he recognized the help he used his length and athleticism well. I think once he gets into an instructive system he'll turn into a good team defender, and he's already a good man defender.
3) Conditioning. Kuminga seemed to wear down as the G-League season carried forward in a way that Green didn't. Of course, I think Green has superstar athleticism. The G-League season was super compressed because they were doing it in the bubble and I think they were playing close to 5 games a week, so this was way more than Kuminga was ever used to playing. This is something to keep an eye on. Kuminga is athletic, but he's not slim, he carries a lot of muscle weight, and we'll have to see whether he can shoulder a 35+ MPG workload at the NBA level. That might eat into his ceiling.
4) Hero ball. As some of the folks you refer to mention, Kuminga did play some hero ball on the Ignite team. Then again, that's kind of the point, it was a showcase and he was showcasing to some extent. I think the hero ball looks worse when you miss shots - if he had hit 30% from distance his hero ball would have looked a lot better. At the same time I disagree with the idea that his hero ball in a showcase situation means he's not a team player. He actually was a VERY good passer and made the right pass - usually made it well - more frequently than I'd ask for in a situation like the Ignite situation. So I'm not worried about that.
I think that you've got a pretty good rundown of his strengths, with the exception being that I don't see anybody really acknowledging how good he is at seeing the floor and reacting on offense. He made several jaw-dropping plays, some for his own offense, probably more for assists, that I didn't expect someone of his age and basketball experience to be able to do.
He's young and he's got such a great foundation to build on. I wouldn't be surprised if he turns out to be as high as the #2 player in the class. Kuminga probably has the most bust potential out of the top 5, so I can see why people are pushing him down a bit, but his ceiling is so high and all the markers seem to be there. Also he's a 3-4 swing, which is a position in high demand in today's NBA. If a team needs a dynamic guard then Suggs over Kuminga is probably a no-brainer because I think Suggs' floor is a good deal higher. But for a team like the Kings with a wealth of guards (If we don't trade Buddy, we've basically already got the top three in the rotation set with 30+ MPG players and have Wright and potentially Davis for lesser minutes off the bench) Kuminga would make a lot of sense if we jumped into the top 4.