It's a good conversation, with useful context, but it should be noted that Tatum is going to suffer by comparison of his ages 19, 20, and 21 season TS% average to Dirk and KD's career averages. TS% is typically the worst during the player’s first couple of seasons- KD’s first four years were the four worst of his career, after that is when he really went nuclear; and Dirk didn't really show Dirkesque efficiency until his third year in the league. Holds for Paul George too- his first four years were his four worst TS%. I don't think Tatum's quite at the KD/Dirk level as shooters, but not only are we comparing him to two of the best shooters ever, we’re comparing his first three years to data sets that include the GOATs’s primes. If he shows a similar growth curve, he can settle in somewhere around a 60 TS% for his prime.
I'd also just add that while I get the point of the "lack of elite athleticism or transcendent skill" as a potential limit to his ability to be in the MVP-level conversation, I do think a case can be made that his team defense is his transcendent skill. Simply put, the advanced stats for his defensive impact are unprecedented for someone his age who isn't an offensive black-hole big. Those advanced stats (D-PIPM, DRPM, D-RAPM, D-RAPTOR, D-LEBRON, to name some) have been consistent across his three years, and consistently excellent. I'm certainly biased, but I think that aligns with a general eye-test consensus from people who study the game, and if you check the game threads from his rookie year, a lot of us were marveling at his defensive precociousness before the stats started to confirm it. It's not something that immediately pops to the casual fan, because his defense on-ball is pretty average, but getting excellent team defense from the nail position is simply incredibly impactful in today's game because it affects every action in the halfcourt set
All that said, it's really hard to do both- to be an efficient, high-volume alpha scorer and to impact the game on an All-NBA type level on defense. Lebron, Kawhi and KD have all done it for meaningful stretches, but even they fade on one end or the other (usually D) from season to season because it's exhausting to sustain that level of effort.