There are things to agree with, but a lot to disagree with as well. First and foremost, you're selling Poythress incredibly short. Kentucky needed him to be "the guy" ONE (count it: one) year. His freshman year, he seen 26 mpg, and he ended up with a very solid 11 points, 6 rebounds per game. The next season, he's put behind Julius Randle (who we can all probably agree, was possibly one the best PF's in college that year), so his offensive numbers dipped, namely his 3 point percentage. Something to note there though, he RARELY took a 3 point shot. Averaged less than one per game. Last season, he played out of position, and still only played 20 mpg, and averaged around the same points, because he's able to make an impact with his physicality, his defense (which was best on the team before his injury), and his ability to pound the ball inside. Next year, I see him getting at least 28 mpg, and he should be able to get his 12 points and 7 rebounds, more importantly though, his lockdown defense, and his ability to make rundown plays on transition defense. Poythress may not bring staggering numbers offensively, but defensively, you may not find better in college basketball when he's healthy, as evidence of him holding his man to 12.8% FG% before his injury. Whether or not he hits threes, how little he takes them, will probably depend on the weather that day, and that's fine, because he's probably hitting 4 times as many shots as the guy he's guarding.
To argue with some of your other points though, last year, Kansas didn't come close to holding Kentucky's jock. We return a solid core of the players that contributed a lot to that pounding. Marcus Lee easily had the 2nd best performance in that game, behind only KAT. Poythress had a solid defensive showing, and despite his poor shooting night, he was able to knock down all 4 of his free throws, which came from his aggressive physicality. Ulis showed that he had no issues getting the offense going in that game.
You can say, based on head-to-head match-ups, Diallo is not as good as Skal. That will be the only notable match-up of the incoming class. The others will not play a moment matched up against one-another, so who really cares. I wouldn't mind if Diallo did end up being better than Briscoe, because Diallo will be too busy guarding the guy that's better than he is in that game. Briscoe will be somewhere else on the court most of the time. Bragg may not even see much time in the rotation. If Ellis did slide ot the 3, then Poythress will as well, and Lee will go in at the 4. Last year, Ellis had many, many problems against them specifically.
Everybody seen what they were ranked, but did they really deserve that ranking? No. They visibly struggled a lot last year, and it continued into the post-season. They lose one post guy with no offense, and gain another one. They get a 4 man who may end up spending most of his freshman year thinking of creative ways to keep Perry Ellis' seat warm. Clearly they'll gain experience, but what did they have to begin with that was so eye-popping?
I can see why some would consider ranking KU and UNC up there, but based on the way those teams played all year last year, plus how some players from both teams played 2 years ago (on both sides), you're not convincing me that either team will make the jump from 15-25 range (where both likely deserved to be) to 1-2 respectively. They may be ranked their pre-season, but I don't see it lasting.