It‘s basically a PKI and this design was chosen with the explicit goal to participate in the EU Green Pass project with the goal that all EU members can participate in the same system.

When the the system stands the only bureaucracy will be for an issuer to get a cert from the authority or for an authority to be included in the root.

All the things you describe with the seal and number and system to validate is just as much if not more bureaucracy and is not that far off from the proposed solution.

The difference is there's no hard dependency on centralized authority or any kind of complex web or mobile technologies.

IT is complicated. Many orgs are still running ridiculous old systems. A lot of people don't have mobiles phones, or generally don't know how to use them properly, may not have data services or even an email address. The 'COVID tracer' app issued by gov. Canada has barely anyone using it.

TN visas (NAFTA visas for US/Can/Mexico) are obtained at the border, it's just something stapled into your passport. That's it. And that entitles you to live in a foreign country. We could feasibly do the same with COVID tags.

It's really hard to set up government agencies that operate effectively with all the bells and whistles, it's costly, tons of consultants, tons of service calls & support ... by leveraging the DMV or it's equivalent, you already have most of the infrastructure in place: they know how to check and issue IDs, they have processes for appointments, service calls, queuing, putting out support content that meets standards (i.e. disabled, elderly), actual phone numbers and physical people to speak to for those who are used to that. For the same reason bank tellers still exist.

We used to do some amazingly complicated things without IT.

But your suggestion still involves a hard dependency on a centralised authority. Someone needs to issue the paper form, issue the stamp, make sure every agency knows what is "genuine", issue a "number" to be written on the paper, create a centralised system where that number and your ID is linked and stored so the border people can check the validity of the number, you need to procure all of these physical goods and send them to the locations. AND they have to somehow then make sure that any other country can take that paper and somehow validate that it's actually genuine as well, maybe call a phone number on the paper and ask?

I honestly don't understand how any of this is simpler, less centralised and a benefit to the end user.

If you have a web browser, a printer and know how to copy paste you can issue a pass. The system returns a pdf you can print and hand to the person. No mobile phone, data service or email involved. This can happen at the same place where you get your vaccination.

For the end user and the intermediary at the issuance place it's exactly the same, you get vaccinated, someone enters it into a form, you get a paper to take with you. With the benefit that if I wanted I could get it on my phone and someone in Spain or Sweden or wherever would be able to validate it in a second.