Abandonware is a clickbait title insofar as it normally refers to licenses, not standards.

The idea of the author seems to be that this part of the DOM API that could benefit from backwards-compatible additions. So, by "abandoned", he hints at the headroom for building more table capabilities into the platform.

He compares it loosely to the form element API and the additions it received over the last decades.

In the case of tables, I could think of things such as a sorting, filtering API, but I can't tell whether that's what he means.