The parent post is making the point that a transaction fee is literally a tax. The financial sector is nothing but transaction fees. Their whole revenue model is interspersing themselves into the mechanics of moving money between a buyer and a seller, and charging a cut for it. A world where everyone pays cash for everything, or even has a centralized ledger where balances are credited and debited by the government, or a decentralized ledger on a blockchain where the same happens, has no transaction fees and no financial sector.

They do perform a service for the transaction fees they charge, but then, so does the government.