1) is it a gambing game - NO
2) is it a ponzi - YES
3) do ponzi's keep operating until they run out of funds / new users - YES.
Let me know if I missed anything critical there.
#1 is a yes, based on the answer to #3.
I don't see the issue, everyone wins as long as the game is in play. It's not like anyone is going to say, "Oh I never knew it was a Ponzi."
Let people play in peace. Do you also picket and protest outside casinos? Do you stand on street corners with signs warning of drivers speeding?
What a waste of time.