So what your saying is that a lesson learned by the United States 45 years ago, is just being learned by Russia now? You're confirming that the VKS is that far behind their American counterparts? That's horrible for Russia's hopes of being a true geopolitical rival to NATO in any conventional sense.It doesn't refute, but it clears some misdirected information. You see, the USAF isn't that decisive factor either during the Vietnam war, even though they have the undisputed quality and quantity. It was USAF lessons in the Vietnam air campaign that transform the USAF into the monster we saw in 1991.
The Russian VKS is in their own phase of Vietnam war that USAF once experienced, it will be naive to think that they wouldn't improve substantially as the war goes by, and because they will improve eventually, there is no reason not to invest in more and newer airframes.
The USAF doesn't stop developing and producing F-4 Phantoms just because the F-4s are getting blown by inferior MiG-17 in Vietnam.
Furthermore, I've never suggested that Russia stop producing air frames. In fact, if anything, they need to get their pilots much more air time flying them, so that they know what they're doing. I'm simply commenting on the fact that since Ukraine started receiving even the smallest amount of air defense (and they haven't received all that much in reality) Russia has been absolutely terrified of flying any of their advanced aircraft anywhere near contested Ukrainian airspace.