List of my frustrations on my 1st playthrough

You actually can get tech blocks from derelict ships. Not always though, and generally, no more than one or two. I've seen three a couple of times, but never any more than that, as far as I have seen. (Though it seems like you should be able to deconstruct the generators and hyperspace engines of a derelict ship for the building materials, that would probably make things too easy.)