Yes, they lost the technology. The last Apollo mission was over 50 years ago, the people who achieved it are retired or dead, and engineering drawings alone are not enough to build a new Saturn V (or the landers, suits, etc). Not to mention all of that is outdated technology by now.
NASA is now building the SLS, a modern(ish) heavy lift rocket meant for moon missions, among other things. But for a couple decades in between there was this obsession with the Space Shuttle as the primary launch platform, and the Space Shuttle wasn't of much use beyond low earth orbit. And with the Soviets focusing on space stations after the Apollo landings there wasn't any competitive aspect to going further either.
There were obviously lots of unmanned missions to the moon and other places in the solar system, but manned activity was limited to low-earth orbit for the last 50 years, so the capability to go further withered.
NASA is now building the SLS, a modern(ish) heavy lift rocket meant for moon missions, among other things. But for a couple decades in between there was this obsession with the Space Shuttle as the primary launch platform, and the Space Shuttle wasn't of much use beyond low earth orbit. And with the Soviets focusing on space stations after the Apollo landings there wasn't any competitive aspect to going further either.
There were obviously lots of unmanned missions to the moon and other places in the solar system, but manned activity was limited to low-earth orbit for the last 50 years, so the capability to go further withered.