That plane list is made up of what's available and relatively balanced one side vs. another.
For Soviet planes, here are the numbers they used overall in WWII (which includes a decent number of P-39's, Hurris, and A-20's). Used what we could, and used a P-40 to simulate some of the earlier Yaks/Laggs/Migs.
Yak-9, 16769 (not many in early 1943)
La-5, 9920 (but have to balance, or it would be all La-5's)
I-16, 9004 (we have it)
Yak-1, 8720 (don't have it)
Yak-7, 6339 (don't have it)
LaGG-3, 6258 (don't have it)
La-7, 5753 (not in 1943)
P-39, 5007 (from US)
Yak-3, 4848 (don't have it)
MiG-3, 3120 (don't have it)
Hurricane, 2952 (from UK)
P-63, 2421 (from US) (not in 1943)
Spitfire, 1331 (from UK)
Il-2, 29937
Pe-2, 11427 (don't have it)
SB-2, 6656 (don't have it)
Il-4, 5256 (don't have it)
A-20, 2700 (from US) -- using boston iii as closest match version
Tu-2, 2527 (don't have it)
DB-3, 1528 (don't have it)