> wtf does that have to do with Curiosity program? All of these are 2+ decades old.

That’s 20 years of learning how to design and land things on mars. They wouldn’t have been able to build Curiosity without the past experiences. The Curiosity program itself started in 2002, just a couple years after the missions above.

What people say is that knowledge in the field is extremely hard to transfer, and easily lost. As an example, apparently we are completely unable to rebuild the Space Shuttle and Saturn rocket, even though technology is vastly more advanced today. Each vehicle really is a “program” including all its people and supply chain. This is also something SpaceX is trying to change by building actual production lines for their engines and bodies, not one-off builds.