The author is confusing not being independent one person setup friendly to an oligopoly.

There are plenty of ISPs that offer email services , plenty of small businesses, government orgs, universities host on their own, most have no problems .

Email is still very much small business friendly, it is no longer easy for indie one person setups anymore.

Many industries are not one person shop friendly , that is just nature of the industry, doesn’t make it a racket

Partially. Mail reputation is managed by companies like this:

https://senderscore.org/get-your-score/

This website should get a very, very low trust score, just as the company itself.