Even though it proved to be straightforward and easy to go to the moon within less than 9 years it will be a very different undertaking to go to Mars for several reasons:
(1) The only reason, as we can see it today, to do this is just for the sake of it, there is no economical or technological and very little scientific gain of any kind.
(2) There is not competition between nations today or in the foreseeable future that is even remotely as strong as during the cold war, so there is also little political gain.
(3) Even though the technological barriers can be solved and it might even be possible to do the trip with today's technology (if you are prepared to spend enough), the physiological and psychological challenges to humans going on a round trip that lasts 12 to 18 months without any chance of intervention or abort and with limited communication to the earth during parts of the mission are poorly understood and will dramatically increase the cost of this undertaking, making it even less feasible.
Challenge Joerg W Schwieder to a bet on this prediction!