Metamask is centralized. That part is true. Metamask should be removed along with anything else that remotely resembles a web browser, especially stuff that relies on a web browser which is the complete antithesis of centralization (but oops, I covered too much already 150% more than what the article goes into).

Saying mining is centralized is like saying natural resources are centralized, which may or may not be true, and is not covered in the article.

The article hand waves about efficiency but seems to only be referring to the inefficiency of bitcoin and no other blockchain.

An explanation on why proof of stake is centralized is also missing. From what I understand, it all relies on a bootstrapped list of validators to get the right chain. And after that, it relies on some subset of those validators to not collude.