An analogy (disclaimer I just made this up on the spot, it's not perfect)
A teenager in highschool may take great delight in riding to the dump with some pals, a case of beer, a gun, and shooting rats. Instant gratification, little to no effort, and the target gets screwed over.
The same teenager grows up a little, goes to college, learns a lot more. He goes back to the dump but it's changed. He's more mature now. He can still shoot rats and drink beer but he's opened his mind and it's sad and pathetic for him to do this now.
Using the easy-mode spitfires for a crutch to learn is okay, sure, whatever. But never growing out of them shows a lack of development, IMO, not more development. If you don't fly half the planes in the game with moderate competence by the time you hit the 8-year mark, you've closed yourself off. Once you HAVE experienced more, learned more, broadened your horizons, you usually tend to lean towards a mental fun, not an instant-gratification-fun.
Mental fun not to be confused with "a bad plane" -- but something you have an intellectual enjoyment of, be it for the history, the pilots, the mission behind it (bombing, anti-tank, whatever) -- you don't just go for instant easy kills.
Which famous author was it that said (paraphrasing): "When fun no longer takes any work, it ceases being fun"?
P.S. The line/author was quoted in the pilot of The Invisible Man (Sci-Fi Channel remake many years back). I probably butchered it horribly.