Short answer: it's not that we don't have the technology, its that we don't have a reason to. With very few exceptions, if you can do it on the moon you can do it on earth or in Earth orbit
Long answer: in the space industry/field the moon is incredibly boring, relatively expensive to get to, and adds an extra step of logistics to an already complicated mission profile. Most space related technology advancement efforts have gone into doing things in orbit and there is more to do there than on the moon, it's logistically simpler, and cost is orders of magnitude less. Stuff is still advancing there, think Hubble vs James Web, GPS 1 vs GPS 3, the entire GOES system. In terms of technical challenges, they're far more interesting than anything on the moon, but it's not as flashy/headline grabbing so it's not talked about much.
The US going to the moon in the 60/70s was a rare combination of a win for scientists, politicians, and the people. The political incentive went away since as the USSR space program collapsed so too did political pressure to continue to put men on the moon and "prove 'Murica is better than those damn commies".
In modern times the political incentive is returning with the continued efforts by China to do more stuff in space so we get the Artemis program, but the incentives aren't that strong which is why the program has moved so slowly.
I know all that, it's what causes me the most frustration. In the end the "Greatest Achievement of Mankind" is not much different than a guy jumping to touch the ceiling because they told him "bet you can't reach", and after that, unless they find oil or some shit like that on the moon, they're never coming back.... At least the Americans, since the Chinese do plan to establish "something" there, at least to show they can.
For me, I view Apollo as the highschool quarterback winning the homecoming game.
In the context, its a great achievement. A lot of time, effort, and luck all came together at just the right moment to create an entertaining spectacle. The school is all happy and celebrating, students will remember that moment for years to come. But in the grand scheme of things, it's not that big of an achievement since everyone there will move on to bigger and greater things, except they won't have a student body cheering them on.
I think saying the Apollo program is one of the greatest achievements of mankind falsely puts it on a pedestal and forever sets up all other achievements as being lesser. Makes us all feel like anything that isn't chasing that glory isn't worth it. It's an achievement for sure, but not the biggest. If I had to give the greatest achievement in space technology to anything, I'd give it to either GPS or GOES.
Yeah, there was a period in time where people were discussing Helium-3 as a source of fuel that we could very easily and efficiently farm on the moon, which was seen as a key step in becoming a space-faring species. Okay, so we know where the fuel is and we can get there, so companies can start using Earth fuel to send helium-3 extraction machines, which can then be used to collect fuel for them to use in further missions and eventually, a small amount of helium-3 will be used to fuel a mission that returns with massive amounts of it, so we have a fuel, and now we can start exploring space even further, with people. It was the clear direction to take.