You can't really say without evidence that something's lacking. Opinions are fine, of course, but they're just opinions.
All WW2 single-engine fighters were gimmicky machines, but how hard each type really was differed wildly. If you compare, say, the Biffer and the Stang, you can expect the former to be a handful in comparison, because the landing gear track was narrow and the engine quite powerful for such a small plane. So taken this into account, how can you say something's lacking, or that the FM is immature without producing any evidence supporting your claim?
PS. And yeah, I know, I do the same myself all the time. The thing is, they're all just worthless opinions regardless of who's the claimant ;)