It is easy to call Bitcoin a Ponzi.

The hard part is explaining how it works.

People claiming it has no value, most likely fail to explain in simple terms:

Halving
Difficulty adjustment
Private key
BIP 39
SHA-256
Proof of Work

Bitcoin is an incredibly sophisticated and balanced system, the kind that only a very bright mind (or group of them) could create.

I have yet to meet someone who understands difficulty adjustment and is not optimistic about #Bitcoin.