As a user, I don't care.
As a disabled user with a screen reader, I might care.
As a developer tasked with maintaining it after the original dev left, I most certainly would care a great deal.
Except that as a developer you have access to the original source code where things are well structured. It only turns into div soup after the React/Vue code gets compiled down to HTML+CSS+JS that can run on any browser.
As a developer you maintain the source templates, not the compiled/generated HTML. The HTML is messy doesn't mean the source templates are so.
Semantic web is basically "please think of the crawlers."