We've chewed over what the US could've done post-Apollo and I agree with Hlekkuka, you have to give the civilian sector some skin in the game to want to get and stay in space.
What the STS lads understood needed to happen but didn't quite accomplish was reducing launch costs out of Earth's gravity well.
Barring some work on MOL's/Skylab being more than a passing stunt with leftover hardware and actually being permanently manned, with a useful overarching mission...
some work on a NERVA space tug doing sat retrieval, upgrades, refueling, construction of bigger/better orbital habitats, ...
us conveniently ignoring the oceans and recycling as sources of material NOT needing to go up or down the gravity well with its attendant costs...
THEN lunar/asteroid mining makes sense, especially for stuff like helium-3 or other materials that would be difficult/impossible to find on Earth.
Unfortunately, space exploration and colonization depend on major countries subsidizing them with hundreds of billions to a trillion USD developing the tech and taking the risks (and laying the infrastructure!) until it gets cheap and easy enough for private companies and individuals to start playing.
The USSR had money troubles of its own and the US always balked at the costs without making a respectable analog of the
USS Enterprise, FTL warp drive and all happen in the next budget cycle to show enough progress.
The Euros and Japanese were happy if they could launch probes and satellites.
One can argue what the USA shoveled in defense spending alone from 1990-present could very well have gotten us a space elevator, moonbase with 100 permanent staff, and asteroid mining that provides us with 90% of our global mineral needs if the entire world lived like middle class First Worlders.
I'm not joking, we have the technical and financial resources to do it, just ZERO political will.
Sacrifice the F-22 and make ion rocketry as cheap and ubiquitous as DC-3's were in the 1930's by 2000.
It's a question of time, $$$, and effort.