It's not a theoretical question, we have the events and the outcomes, complete: The time it took from announcement to actually landing on the moon was shorter than the time it took from recognizing the lead problem to banning it from all fuel including aviation fuel. The second one already is longer. So whatever your model of reality, the complete model is reality itself and it proves that point. What else would be better for arguing than the actual real-world outcomes?

If you want to say things like "but there were less people working on the problem" you are removing things from the real world to build a more limited model to fit your argument. Overall getting enough people to work on the problem is part of it. Including everything, which includes getting attention and resources devoted to a problem in the first place, the moon landing indeed was easier. I think it's not much of an argument that exactly that, getting a vast effort rolling and people and resources devoted to a problem, really is one of the hardest problems. It was pretty easily achieved for the moon landing.

If you want to separate the policy problem of getting the resources from the technology problem you are only looking at a part, to get the desired outcome both are needed. Sure, the technology part was harder for the moon landing - which makes it even worse that the other part, the policy stuff, is so hard to accomplish.