The important thing is roles, not positions. LeBron is usually a PF officially, but he controls the ball for the important possessions like a traditional point guard would. Wade was the secondary creator/scorer and Bosh, Battier, and Chalmers (or Ray Allen/Mike Miller) were just there to space the floor, defend, rebound, and be glue guys. Because Wade was so good at everything else and also Bosh was a good 3 pt. shooter for a big, it wasn't a huge deal that Wade wasn't the best long-range shooter. Besides, these comparisons where you invoke Jordan or LeBron don't work because they are anomalous, once in a generation players. Tatum's obviously never going to be as good as either and let's not even mention Jaylen's name next to Pippen or Wade (oops).
The comparisons to Kawhi and George are more valid, in that they both desperately need a guard that can facilitate. That's why the Clippers keep swapping point guards in an effort to get their offense unstuck. The Bulls have the same issue, scoring but no creation. That's why they fell apart (also no defense) when Ball got injured. It's why for years people wanted the Celtics to get a true point guard next to Brown and Tatum.
If you don't have that one elite creator like a Luka, LeBron, or Jokic to run your offense around, your team needs to be elite in other areas (like a dominating defense and a couple of great one-on-one scorers), or play a more IQ-heavy team game to generate points. If Curry started getting tired of running around and thought, well I can get 30 most nights just taking it easy and scoring on my own, he could probably do that. But it would also make their offense a lot more one-dimensional and predictable. The Warriors leverage the attention he receives to open things up for others, but it's not just on-ball, but off-ball as well. Obviously, this takes a tremendous amount of buy-in from a team and also a level of unselfishness most teams can't achieve. The Spurs are another example of selfless, team basketball because they had a rare unselfish star in Duncan and then got guys who were used to team ball in Europe. That's the squad that Stevens keeps wishing he could re-create.
So, it's not just Tatum and Brown are wings, but they are wings with similar skill sets and weaknesses. Both are scorers first and foremost. When they have the ball, their inborn instinct is to score. That's just how they're built and what they're best at. Sometimes you have guys who have the ability to score but love passing just as much. That's not Jaylen or Jayson, which doesn't help matters. They also both aren't elite ballhandlers. Tatum is better than Brown, but both aren't good enough to be lead ballhandlers. Furthermore, Tatum is a better shooter but both are definitely rhythm guys who needs attempts to warm up (Tatum being more efficient this year is welcome). Jaylen isn't Ray Allen, who easily transitioned into more of a catch-and-shoot guy on the Celtics and the Heat because he was always an elite jumpshooter. Brown is someone who has had to work a lot to become a decent-enough shooter, but it's not like he's competing in the 3 pt. contest. Some games, his 3 ball goes in without touching the rim. But then other times when he's off it looks like he's never shot a ball in his life.
Add in the fact that both are naturally quiet and reserved personalities and not natural-born vocal leaders and it's not surprising that Celtics fans thought we'd have to split them up eventually. Remember, this is before the recent arms race and most teams were still built around 2, maybe 3 stars. Nobody really thought it was possible for the Celtics to keep adding top pieces around Brown and Tatum not just from a cost but an asset perspective.