Here's my take, having been here since 2010, and another 10 years in Fighter Ace prior to that.
We have maybe 50 fighter pilots left subscribing. If even that. The rest are WW2 players, who only fly planes to serve the war purpose in one way or another and don't really engage in any prolonged furballing. They're quick to jump in manned guns and GVs when enemy planes arrive.
Of those 50, maybe 10% are highly skilled, typically winning 90% of their engagements, regardless of their disadvantage. They'll be in the G6/K4, Spit8/9 and F4Us, sometimes Ki84 or Jug. Then there are about 20% who are skilled in SA, but less so in ACM. They fly very carefully, prioritizing survival, and only engage if they have substantial advantages. This is where you find the Tempest, Yak3, 190D and P51.
The other 70% are 1:1 players. Almost no chance of beating the 30%, but can find occasional fun burning around in Yaks, Spixteens and La7s, killing Brewsters and Zekes, or anyone else that gets caught up in an engagement or is unable to dodge the merge-HO.

There are of course exceptions, but that's my random take on what's left of the air combat aspect of this game.
I don't have the answers on how to fix things. I watched the demise of my other beloved game, despite the huge amount of changes and efforts to respond to the community's wishes, right up until the end. I see the writing on the wall, but I still plan on being here until the end. Despite some folks' belief that it's the "uber" pilots that cause people to quit, I submit that it's the dedicated dogfighters that help and support squaddies and teammates that are sustaining this game.
I think smaller maps with more concentrated fights would certainly help. Getting rid of LW birds won't make any difference, since there will still be one plane that is faster than the others.
I still love this game for those rare nights that there are good fights. There's just nothing better than a sustained furball with close bases (Northco) or CV battles so it stays low and fast. It is sad and frustrating that air combat is the exception now. I can't tell you how many times already this month I've upped for a sortie, flown around for 30+ minutes without squeezing the trigger. That happened tonight, which is why I'm sitting here blabbing on the BBS.
But I will keep trying and keep hoping for that one good night, or even the one good fight, which makes it all worth it.