The 1960s was a decade of rapid scientific progress, probably because lots of weapons research was carried out during WW2 and the early 50s after the nuclear devices were exploded over Japan, and the technology suddenly spread outwards into civilian life.
The OP is right in many respects, progress has stalled. Just think of the Wright brothers first powered flight in 1903, and 66 years later man had walked on the moon.
A similar period of time elapsed between City Of Truro and the bullet train.
Why no equivalent progress in the last 40 years? I think mainly because rich philanthropists have become a very rare species; the wealthy prefer to make even more money for themselves, and governments have poured billions of taxpayers' cash into ever more complex military hardware to fight ever more unwinnable wars.
Instead of which, they should have been putting all their efforts into finding a cheap and easy way of escaping from the Earth's gravitational forces.
I realise that the purists will be horrified, but I would pile a whole shed load of the nastiest bacteria we can find and send it on a rocket programmed to land it on Mars. Then just wait and see if anything happens.
After all, there do not seem to be any other intelligent life forms in our Solar System, so we might as well experiment with the nearby planets and see if we can encourage some form of colonisation as quickly as possible. We cant do a much worse job on Mars and Venus than nature seems to have managed already.
I do not subscribe to the view that we should sort our own world out before messing up another one, because we learn more from making mistakes than just faffing around trying to look clever.