If semantic HTML is important for accessibility and for software to be better able to parse information out of it, and AI solves the latter, semantic HTML is now less important because some of the use cases that needed it previously no longer need it. If you take "less important" as a moral/value statement instead of in terms of total utility provided, and assume that AI will have zero accessibility benefits, it will merely be as important as today, which is still at odds with the assertion of the original article that it would become more important. N.B. this seems doubtful, given how e.g. you can now past a bunch of code into an LLM and ask it questions quite naturally -- something I can easily see adapted to e.g. better navigating apps using only voice and screenreaders.