PoW is not a ponzi, if you have any understanding how PoW works then you will know this is the case.
PoW will only be inflating until all of the units have been received via the block subsidies at which point the miners will receive block rewards from TX fees, which is the same how PoS coins reward their "miners"
If people stop buying BTC then miners will stop mining. How is it different from a ponzi scheme?