The moon is a lifeless rock with nobody on it. That seems like a better place for garbage to go than the earth. And since it's going to impact the moon at 2.43km/sec, I don't think there will be much visible stuff remaining, just a crater and some bits of aluminum.

Also what's the alternative? Moon missions don't have enough extra propellant to go back to earth and deorbit. They might have enough to move to a relatively stable orbit, but then it's just long-lived orbital debris.

That's the neat thing. Dumping on the moon or anywhere (other than Earth) isn't possible, as the litter is infinitely more valuable than the existing dust and rock. It's as if someone was dumping gold bricks into your yard. You really wouldn't mind at all, and would ask for more. The only exception would be radioactive waste, as that is less valuable than the surrounding dust and rock.