The Japanese built some very innovative and excellent aircraft during the war. Designs like the Mitsubishi Ki 46 or A6M Zero were tremendous aircraft for their period. Yes, they lacked armor and other protection but, the Zero for example had an equal armament to that of the Me 109E, nearly double the range, was about equal in speed and, had far superior maneuverability.
Kawanishi's N1K1-J and N1K2-J Shiden and Shiden-Kai were the equal of almost anything the Allies were flying late war even if a bit slower.
I would contend that Mitsubishi's G4M bomber (the Betty) was every bit the equal and better of the He 111; the Luftwaffe's mainstay. Certainly, its heavy defensive armament of 20mm cannon was vastly superior to the 7.92mm paint chippers of 1940 Henkels and Junkers.
I have no idea were you get the idea that their "guns jam alot." This is not any more applicable to the Japanese than it is to any other combatant. There were certain aerial weapons that were prone to jamming like the German Mk 108 30mm or the US Pontiac M2 37mm to name but two.
I would not characterize the Japanese as "crappy" in their general war effort. True, they were handicapped by lack of an abundance of raw materials and often by lack of research, development and, production facilities. But, these did not preclude them from producing many innovative and in some cases outstanding aircraft designs. Nor did it preclude them from at least an understanding of technology even when they could not produce any quantity of it.
They beat the everyone to developing centimetric radar, including the British, but couldn't put a useful set into production due to lack of resources. Germany only managed to get a set into production in 1945 just before the war ended.