>Access to a single ancient reactor would give you the equivalent of decades of mining from any single uranium site
What could is uranium to destroyed civilisation where all previous knowledge has been lost? I don't think future post civilisation peoples are going to be reconstructing a nuclear reactor from wood.
>You can literally walk through a demolition site and pick up rebar and aluminum by the ton
Post civilisation people are not going to have much use for demolished materials. Yes with modern technology we could reuse it. But how will they use it? I've seen a build demolished in the third world. People came and got the pieces of rebar true, hammered the concrete off it, but only to sell, not to use. I don't really think in a post civ world it would be of much use
> It's not impossible to imagine a future society skipping liquid fuels (and most of aviation) and still making its way to the renewable revolution.
Impossible? Perhaps not, but still very very unlikely. For decades after the event, survival will be all encompassing. Knowledge will pretty much have disappeared. You talk about skipping liquid fuels and aviation and going straight to renewables. First people will need to invent electricity again - everything will need to be "invented" again from a much weaker starting point. I just don't see it happening. Much more probable it is the end of human civilisations / humans as the dominant species on this planet