From this, its evident that the CM team made absolutely zero efforts to explore options for a TBD substitute, and decided to go with the TBM, which is known to be just a horrible substitute for the TBD.
Not exactly.
It is true that the TBM is a much better plane than the TBD. For that reason, and because Coral Sea and Midway are major WWII battles and the subject of scenarios, the TBD is one of the top 5 planes I'd like to see added to the plane set.
It is also true that the B5N is a better fit in terms of airspeed.
Payload doesn't matter because all US torpedo bombers in Coral Sea and Midway scenarios use torpedoes.
However, the B5N is, I suspect, less sturdy than the TBD, has no forward-firing gun at all, and would have Japanese skin in the scenarios (because of how skins are implemented on the servers). So, immersion of having a bunch of Japanese-marked torpedo bombers has to be considered, along with those other factors.
Also, we have tested TBM's in several runnings of Coral Sea, and it is not unbalancing at all. In those runnings, the IJN side has done about as well as the US side. What ends up mattering is whether or not there is CAP and, if so, whether or not there is strong escort. If there is CAP and not strong-enough escort, the TBM's get annihilated just like B5N's do. It boils down to the fact that, whether you are in a TBM, B5N, or TBD, you are approaching for a considerable distance on the deck at low speed, so top speed of the plane ends up not mattering much in actual runnings of the setup.
So, some of your points are correct, and are not a surprise to or ignored by the CM team, but you are missing some other points that we need to consider. Your preference on which set of things is more important isn't wrong -- but it is your preference, that one set outweighs the other.
HTC will add the TBD at some point, I bet, and we won't have to pick.