I highly doubt that 50 years ago there were microcomputers capable enough to land a rocket like the Falcon 9 propulsively on Earth. This requires extremely low

I highly doubt that 50 years ago there were microcomputers capable enough to land a rocket like the Falcon 9 propulsively on Earth. This requires extremely low latency, even prediction, much like balancing on a stick. The basic idea an algorithm is simple, but you have to deal with a lot of uncertainty. Buran automated landing is a different thing and more in line with aerospace autopilots. DCX was thirty years ago, used cutting edge technology at the time and didn't come back from anywhere near orbit. Reuseability has largely been rejected as too difficult, costly and risky. SpaceX has had a tough time showing it can work, most of the other companies have not yet succeeded.