It's important to take a step back here and remember that the web did not start as accessible, nor did any of the native desktop UI frameworks. The author suggests that the only way to "fix" Flutter Web is to throw it all away and start over, which is just patently false when comparing to the history of the competition. Not only would it be ridiculously easy to make Flutter generate semantic HTML without changing any of the core functionality or interface, but in fact HTML already features a widely-used solution for exactly the use case the OP focuses on [2].
The author also tries to take a stab at Flutter initially for attempting to replace HTML, but I think this is another misunderstanding of what Flutter is trying to accomplish. The goal is not to replace the web with something else, but instead streamline creating web apps (in much the same way as React, Vue, etc.) With that in mind, many of the criticisms stop making sense -- are people really expecting CSS restyling tricks and Vimium to work in modern web apps like Google Drive or Discord?
To take one (rather sneering) quote out of the authors playbook:
>To end I’d like to leave you with a quote from Dr. Ian Malcolm.
>Your scientists were so preoccupied with whether or not they could, they didn’t stop to think if they should.
[1] https://flutter.dev/web [2] https://developer.mozilla.org/en-US/docs/Web/Accessibility/A...