You're flying it wrong or flying the others more correctly, or some combination of that. Additionally, the spit16 thrives in furballing, whereas half or more of those other planes don't work in situations where they can't escape for E, such as knee deep in furballs. That means you're that much more removed from kills, instead of having them directly near you and at slow speed, IOW just a few seconds from dying. You have to manage your fights further to the BNZ side of the spectrum.
Asking why the P47N or 190A8 doesn't have a K/D comparable to the Spit16 is disingenuous. K/D doesn't tell the whole story. It doesn't reveal that, for instance, the Tempest just trims the furballs at high speed because it would get mauled in a slow knife fight, including because it's a perk prize. The Spit16's admittedly no level speed champion, but it does have top tier climb and E retention, which allows it to be competitive at high speed. That means it's got just a marginal disadvantage in its only weak area.
Read the topic: "the spit16 is a noob plane". That means easy to use, forgiving, and possibly lethal with little effort. All of which it is.