The web doesn't need gatekeepers the way you don't need a bank account, driver's license, or a credit card. You can do without it, but it sure makes it harder to interact with modern society. The days of the mainstream internet being a libertarian frontier are more or less over. The capitalist internet is firmly in charge.
The real question is whether there is more business opportunity in supporting "unsigned" agents than signed ones. My hope is that the industry rejects this because there's more money to be made in catering to agents than blocking them. This move is mostly to create a moat for legacy business.
Also, if agents do become the de-facto way of browsing the internet, I'm not a fan of more ways of being tracked for ads and more ways for censorship groups to have leverage.
But the author is making a strawman argument over a "steelman" argument against signed agents. The strongest argument I can see is not that we don't need gatekeepers, but that regulation is anti-business.