Hurricane, C 201 EC, Mig-3, P-38E in Tunisia, RE 2000, Fw190A - all fighters with no air-ground ordnance…
Certainly such things were used a lot - but in the context of this game - based supposedly around infantry actions - they are a collosal waste of player time. And because of that they are a waste of Dev time too.
Yes, all those planes are only needed to shoot down an enemy one and get out of the cockpit. No motivation to stay in the sky
Another serious issue is that german 20mm guns are peashooters. The damage they deal is pathetic. You empty all your ammo on an enemy plane, and it is still flying, no problem.
Not so - try being one of those enemy planes and see how much damage it does.
All planes take way too much damage - a Il-2 can empty 2 x 20mm into a Stuka and not instantly shot it down…
But hen yesterday I shot down a Il-2 with a 123 - took 2 ammo loads to do it, but he obliged by turning easy circles in front of me - death by 1000 8mm holes 
Yes. I did. Very often. The damage plane take is from the ground. I do not care much about german 20mm guns. It is not uncommon to get set on fire or pilot sniped by ground player or AI troops. I took down quite a few planes with bolt action rifles before the accuracy nerf.
Bollocks
If you think 20mm guns are fine, you must be playing a different game.
The issue with planes is their awful damage model and their flight model which can randomly be fine or become completely unflyable 5 minutes after taking damage.
The normal survivability is what you see in Warthunder or DCS. If 0.2-0.5s of burst fire from 50 cal ammo and higher calibers hits a plane, it cuts it in half.
All of the planes in this game are flying tanks; and without upgrades, half of them struggle to stay airborne.
Most of the planes are also completely pointless, because the maps are too small for bombers, and most of players were annoyed with them. No one plays bombers, unless they kamikaze, so there is no reason to play fighters either.
Just as with mortars and radiomen, planes are niche squads, because that is what the community wants.
I get shot down by German planes in Moscow all the time - if you think the 20mm guns are doing no damage you are deluded.
And yes - the damage model is borked - long known - that is not teh same as 20mm guns doing no damage as you assert without any evidence, and indeed against the implication of your last post!
Moscow is not a measure of how planes are in this game. You literally get cardboard planes for the Soviets (both the yak and the i-53 are made out of wood), and stukas which can barely stay in the air. IL2 does not have this problem, and it turns well enough to reverse bf109 for no reason at all.
Although, that is the type of damage all planes should be able to sustain. Not much, at all. Like some of the planes in the Moscow campaign.
The damage model is very different in the other campaigns, where the only planes which do some consistent damage are the ones armed with 50 cals (Normandy, Tunis) or russian 37mm (Berlin).
Every other gun in these campaigns is trash. Unless you set the enemy on fire, or pilot snipe, you are not taking anything down, except Stukas, which fall out of the sky after taking a bullet.
The whole air thing is terrible. Bombers/attackers are barely useful, unless they have rockets. And fighters serve no point, unless someone is flying an attacker with rockets and isn’t doing a kamikaze.
Moscow is German 20mm and 7.92mm as the only airborne guns.
But if you like - here’s me getting hit by 20mm in Berlin and not being wiped out…
Get over it.
the air meta does seem very ad-hoc.
but this is also the team that gave us casemate tank destroyers as the lvl 22 unlock in an urban campaign, so are you really surprised.