Let's start with the offense argument. You're using numbers to pass Tatum off as similar to LeBron/Kobe/Wade but they aren't as close as you'd think. First, you have to account for era. Second, you have to account for pace and minutes played. On a per 100 possession basis, Tatum falls well short of those guys.Tatum is 33-10-4 this season, LeBron is 37/10/10 for his career, Kobe 36-7-7, and Wade 34-7-8, without factoring in era or scoring efficiency. Again those are career averages, not primes. Tatum's 33-10-4 is more comparable to Brandon Ingram's 33-8-6, than those other guys.
I have no problem issuing absolutes when the evidence isn't there to suggest something will happen. Passing/playmaking is like athleticism, you can improve it but the elite ones just have it. If you don't, you never will. Luka is an elite passer/playmaker, Tatum isn't and never will be. That's not to say he can't be good at it (something I've backtracked on with him) but the difference between good and elite with passing is massive. The foundation of great offenses are guys who are elite scorers and elite playmakers (or great coaching).
When going into IT/Trae/Luka, the thing is the more you look into them the less comparable they are. They only look similar statistically from a simplistic view of bulk numbers. Per 100 with advanced stats:
Luka: 41.5 ppg 13.5 rpg 12.7 apg (46-32-76) 6.1 topg TS 58.5% PER 27.6 BPM 8.4 VORP 5.4 (shortened season) RPM 4.28
Trae: 39.1 ppg 5.6 rpg 12.3 apg (44-36-86) 6.4 topg TS 59.5% PER 23.9 BPM 3.9 VORP 3.1 RPM 0.97
IT: 42.4 ppg 4.0 rpg 8.6 apg (46-38-91) 4.1 topg TS 56.2% PER 26.5 BPM 6.7 VORP 5.6 RPM 2.48
Which of those guys are you taking? The numbers suggest you take the first guy pretty easily. He also happens to be the tallest, best defender (by a mile) and the youngest player in that group as well. I don't think it's particularly close and that's comparing him to Trae Young (a young star) and peak Isiah Thomas who was 2nd team All NBA that year. Funny enough, Luka already has a 1st Team under his belt which is more than both of those guys and Tatum combined, and he's younger than all of them. Also, I'm a huge proponent of Trae Young and firmly believe he's a top 30 player in the NBA with a chance to eventually be top 10. He's unfortunately saddled on a miserable team that went through an abundance of injuries this season but I see him being a superstar for years to come.
I don't see the point in bringing up Westbrook because he doesn't understand basketball. He's a stat accumulator. Luka is a basketball genius. Look at the difference in their play this postseason. Westbrook handicapped the Rockets, while Luka (a decade younger) played fantastic and forced a competitive series with a heavy favorite. They are in no way comparable except in terms of raw numbers. It is true that Dallas did have a good offense this season when Luka was on the bench. That is not mutually exclusive from him being "the system" in Dallas. Rick Carlisle being a great coach and bench guy does not mean that Luka isn't the system. A one game sample size against Milwaukee doesn't show anything, they were essentially 7-9 without him and 36-23 with him.
If Luka went to Boston, the offense would look different but would still heavily revolve around Luka, far more than it does Tatum. He's a much better on-ball creator, it's just logical to do that. We seem to be arguing different things. If I understand correctly, you are suggesting Luka is in an enviable position and puts up gaudy numbers because he's forced to be the man. Again, if I understand right, you say Tatum plays on a better team and thus his role/ability to produce numbers is restricted. I'm saying Luka would be the man anywhere because he's that good. Every system, like with LeBron, would cater to Luka no matter where he is. The numbers that come along with that are secondary. I'm saying Tatum could not do the things Luka does because he doesn't have the skillset to do them. It's not a numbers argument, it's a running an offense argument.
I think I misspoke with Nash. Obviously him being a better defender helps, albeit I think it's largely negligible. To better explain my point, what I meant to say is that if you made Nash 5% worse on offense and 5% better on defense (pick any % you want), the team does not get better. His offense was easily the most valuable part of those teams, and no matter how good he was defensively, the foundation behind him would keep them from being a good defensive team.
Semantics aside Kobe lite seems relatively doable, I don't think he'll be the scoring talent or quality of facilitator Kobe was but he certainly seems more willing to make plays for others. I think his play-style is more PG 2.0 or Durant lite though.
I don't know how to find Bubble only stats (though Luka was 1st Team All-Bubble), so let's use the current season and postseason for these guys. The gap between these guys offensively is pretty large, and that's a big part in why Luka at age 21 made All NBA 1st Team and Tatum made the 3rd team (albeit should've made 2nd, still he had no argument for 1st). Remember that Luka also played a straight up better opponent in the postseason.
Per 100 possessions:
RS: 33.0 ppg 9.8 rpg 4.3 apg (45-40-81) 3.3 topg
PS: 32.1 ppg 13.2 rpg 5.4 apg (44-41-79) 3.2 topg
RS: 41.5 ppg 13.5 rpg 12.7 apg (46-32-76) 6.1 topg
PS: 40.7 ppg 12.9 rpg 11.4 apg (50-36-66) 6.8 topg
The numbers aren't close. If KP was healthy, it's certainly possible that they send the Clippers home in round one. Simplifying it down to "this guy won a few series and this guy didn't" isn't analysis. Tatum has never beaten an opponent in the playoffs at the level of this years Clippers. So he's played easier opponents, been in the league longer, been on better teams, and was a role player for some of those wins. Again, any time Tatum has played a team on the level of this years Clippers he lost. Luka's performance in his one playoff series against the Clippers is better than any Tatum has had. That's not all that arguable.
I'm not sure what you are bringing into the argument by saying basketball is position-less. That only helps Luka. he's nearly the same size as Tatum and has guarded 1-4 as well (albeit as a way to hide him). Tatum is a better defender but Luka guarding different positions isn't an issue. He's a PG on offense being he's too skilled to be used anywhere else. He's already better offensively than virtually every player you named too. Luka is primed to dominate the NBA for the next decade plus. He's younger than Tatum, he made a much larger jump from year 1 to year 2, and he's already better than him. Based on what we've seen it seems likely that the gap only grows going forward.