If those statistics are to support your argument then you have to establish the correlation that too many late war planes versus early war planes are causing low numbers of players. And you can't.
I'm not saying they are causing low number of players, i'm saying that the game can be potentialy more enjoyable when all of the planes will be used on arena in a distributed fashion which can lead to more players (with 2 sides and AvA) because the plane rotation will be higher (more variants of planes being used in the arena)
The statistics show what is in the game - not to support arguments. It's the other way around, i base my arguments on what I see on the statistics.
Statistics show that late war planes are used in 80% in arena, mid and early war planes take the other 20%.
It would be more natural if planes were distributed in orderly fashion. Early war taking 40% mid 30% late 20% and 10% 'top planes'