"Decentralised" is the most abused word in the industry. The useful question is binary: can anyone change the rules, roll back the chain, or print more? If yes, there is a centre. It does not matter how many servers they rent.
The five questions
- Can an ordinary person run a full node? Bitcoin: yes, on a laptop with a cheap drive. Many chains: hardware costs thousands, or only a few hundred nodes exist, or "nodes" trust a company's servers.
- Can anyone produce blocks without permission? Bitcoin: buy an ASIC. Many chains: a permissioned validator set, or a stake minimum that excludes almost everyone.
- Is there an entity that can change the rules? Bitcoin: no; changes need broad node adoption and take years. Most chains: a foundation ships upgrades on a schedule.
- Who holds the supply? Bitcoin: distributed over seventeen years of mining and trading. Many chains: majority with founders, funds and the foundation.
- Has the chain ever been rolled back by a decision? Bitcoin: no. Ethereum: yes, in 2016, to reverse a hack, by decision of its leadership.
Why it matters for money
Money needs to be the same for everyone and changeable by no one. A system with a centre will be used by that centre when it matters: to bail out insiders, to comply with a government, to fix its own mistake. That is fiat with a blockchain.
CHECK YOURSELF
pick an answer for each question