Sure, but once something is acted upon their will be a change. The moon is also mostly comprised of titanium and lithium, some of the lightest elements. Sure, landing to plant a flag might not do much, but constant travel, or even strong magnetic forces required to generate power may have lasting consequences.

Yea ya know, all of space let’s just fuck with that very light object not secured by contrifugal force and no atmosphere to cushion forces, like the mass of a nuclear reactor landing on it, that our climate is highly dependent on. Ok.