While the level and experience do have a lot to add to context of "crutch" some planes are just easier to fly regardless of their turning abilities.
I wouldn't say a spit5 is a noob plane in the MA. You should have seen it 6 years ago before they chopped the plane in half, it was a monster. The Ki84 and F4Us can easily be out ran, while I personally believe the F4U takes a lot of experience to be good in and the Ki84 is mearly the trainer, although you still have to set up kills when attacking high from a base, and in the FSOs its tough vs the high american planes. Planes that cannot dive well in the game are huge degrading factors which is why I don't consider any of the 109s a cruch plane. The K4 is about the easiest one to fly, but you have to set up shots with the plane and that takes an experienced pilot, you cannot just BnZ for easy kills in the K4 and expect to get a lot of kills.
The P51 and 190D can easily run away when they lose advantage. It happened to me about 8 times yesterday. IMO that is a huge crutch. My plane cannot run away sometimes, so I get caught by yaks and 190s in my G2 then have to fight the BnZers and all the others that choose to jump into the fight. Since my plane cannot extend away I may get caught in the gang. Therefore the situation becomes more challenging and I have to use expereinced skills to maybe win the 3 on 1 but many times I don't win when 4 planes jump me. That is the struggle with flying slower planes.
Speed is the biggest crutch in WW2 planes or aviation in general. If you got a fast plane and fly it fast no one can catch you and using E to avoid or rope planes is the essential tactic to these planes.
And Joachim I hate the A6Ms too! Thing can turn and then climb so well! You want to fight them but they are just like Nat's!
Like I said, if a player is using a plane as a crutch, then they should be rather easy to beat 1v1. If they're not, then it's not a crutch. Therein lies the basis of the argument. To claim a player is using any plane as a crutch, when that player could beat their opponent easily same plane vs same plane, does not pass the logic litmus test.
Now, if you're saying that a crutch plane is used to survive multi-plane encounters, that argument is flawed as well. Any two planes, flown correctly (Robert Shaw outlines this very well in his dissimilar aircraft tactics section), will end up in a relatively prolonged engagement. Therefore, to claim that a plane is crutch because a player is using it to survive a 1v2, 1v3, etc. is backwards.
If you're routinely surviving 1v2's and 1v3's, etc., it's not because you're good, it's because your opponents are terrible. You outlined this quite well in your 1v3 video, where all of the opponents tried to turn with you. Had any one of them broken off and built up speed and came back, you'd have likely lost. However, none of them did. You won because their flying was incompetent (not to detract from your own skill whatsoever), not because you necessarily outflew them.
Ergo, the idea of "needing" a crutch plane to survive in a multiples situation is based on the idea that a pilot can take on two equally-skilled opponents and win consistently. That is not only illogical, it contradicts everything learned in ACM.
It all goes back to ACM 101, energy vs angles. If you don't "need" a fast plane to fight multiple opponents, then your competition sucks (sorry, it's the truth). Now, you may think/feel/believe otherwise, but I'd be willing to take you in the DA with me and Kruel and do several 2v1's - you wouldn't stand a chance. And it wouldn't be a reflection of your skill, it's simply ACM tactics. A single opponent cannot win against two competent opponents in similar aircraft (barring the rare one-in-a-million lucky shot scenarios that can occur for any player).
So we're back to my original point - a plane can only be a "crutch" if it's needed to win 1v1. And, truth be told, there are several crutch pilots (ROCKY comes to mind with his runstang). However, it's the pilot that makes the plane a "crutch" plane, not vice-versa. If said opponent can beat someone else in like planes, then the plane isn't a crutch whatsoever.