So what if there are a lot of P-51D's flying? There is nothing wrong with that.
That's the reason the playerbase is so low today - gameplay, because after years of playing many people found out what many people said over the years, and they left becuse nothing was changed.
The graphics improvement did not bring back many new players and they will not.
Look at counter strike, it's a game from from 1998, the graphics are very old, but the gameplay is same awesome as in the day and it has many players playing, and is one of top games played on Steam, the 3rd iteration CSGO has over 600,000 people playing at same time.
A game is about gameplay first.
For example, the P-38L is a late war P-38 but does not unbalance the game compared to the P-38J, a mid war plane.
A p-38L or J unbalances the game vs spit 1 or I16, a early war plane. late > mid > early
"Everyone" isn't flying late war planes,
Sorry but statistics and numbers tell the truth.