Well if the resources (metals power sources) are from another planet would the technology have ever been possible? seriously would the poor little humans be stuck forever on earth because boo hoo we don't have any unobtanium as unobtanium/ramonite is only only on the yeerk/taxxon/whatever home world?
The answer is no: an innovative mind can adapt to the physical circumstances and find local equivalents: it is like you're cooking a recipe from another country and it asks for an obscure ingredient that isn't available in yours: so you do a little research and substitute with something local, it wouldn't be the same, but it would be innovative and original and originality and innovation are what distinguishes humans from Yeerk parasites. and sure you or I might not be able to so but you're acting like all humans are equal: we're not, we have equal rights but some of us are smarter then others and such geniuses might well (especially after the controller experience) be able to copy yeerk technology. and whilst nuclear power might not power a dome ship, i am certain it could power a dracon beam, perhaps a battery (as in a resource that doesn't sterilise the user) could as well...