I just realized something.
Arnim Zola and SS-Hydra manage to make all sorts of ray guns pew pew shit within months of the Red Skull looting the Cosmic Cube/Tesseract from the Norwegian Monastery.
....Meanwhile, SHIELD (and it's precedessors) have had the CC/Tesseract since 1945, after Howard Stark fished it off the ocean floor.
So...where's the ray guns based off Nazi Technology equipping SHIELD's battalions of meatpuppets?
It's called "Phase 2" and they have it in storage, but are breaking some components out.
Apparently, unlike the Nazis
, SHIELD was not given the go-ahead to build ray guns as soon as they got their hands on the Cube. I'm not surprised by that. Remember what happened with Hydra: they betrayed the Germans and started fighting their own private wars. If you were part of the shadow civilian oversight committee for SHIELD... I don't know about you, but I'd be very reluctant to risk letting history repeat itself by giving SHIELD first dibs on ray guns and Cube-based WMD.
So they just get told to sit on the Cube, and it gets filed in the same warehouse with the Ark of the Covenant and whatever.
After weird shit starts coming in from outer space, suddenly developing all this stuff becomes much more urgent. Just as the Manhattan Project was in large part a reaction to a specific fear (German bomb), "Phase 2" might have been in large part a reaction to a specific fear (alien invasions we can't tackle with normal weapons because if Lieutenant Mike Wong says BALLS to the aliens with missiles, they will say BALLS right back and laser-vision his jet or whatever, then fold up our missiles and wear them like silly paper hats
Another possibility is that Hydra knew something fundamental about the cube that we don't, because they got it by translating some bizarre alien artifact or whatever, which CAPTAIN AMERICA subsequently crushed under his shield without realizing it. Before SHIELD could tap the cube's energies they had to, say... I dunno. Invent quantum electrodynamics? Make advances in chaos theory? Develop more precise instruments for X, Y, and Z?
Whatever, the practical upshot is that SHIELD needed a lot of time to catch up with Hydra's position before Hydra had the cube.
Zola had all kinds of weird technology going before he even got the cube- the problem was the lack of a suitable power source.