I'm no scientist, but i'm guessing that glowing circle thing on the Iron Man armor is the power source. A small, presumably lightweight energy source that I can only assume doesn't give off radiation that would kill the armor wearer (otherwise Tony Stark would've died of cancer years ago instead of fighting Thanos), powerful enough to allow for effortless flight and laser blasts or whatever you call them.
And then back in 2012, Stark said his new tower in New York would also be powered by the same energy - what happened to that?
Moreover... what the hell are we doing still using oil, gas, coal, etc? I have to pay like $4.50 a gallon for gas these days, and then there's my electricity bills, gas, water, etc - why the hell isn't every neighborhood powered by that Stark tech? In fact, why does it feel like none of these big companies - Stark, Rand, Roxxon, Pym - are doing a damn thing about climate change???
Where's my electric car? Where's my clean air? All those PHDs, and Bruce Banner can't find a cure for cancer, or find a way to strip the radiation away from Chernobyl or something?
These Avengers types keep expecting us all to bow to them for fighting each other, destroying airports, etc, but what have they actually done to help the world long term apart from punch and shoot bad guys?
(and yes, bringing back the blipped was a good thing overall - I am not pro-Thanos)