When Sir Bruce speaks up, you'd better listen. That's the law, son.

(…) If the importance of good HTML isn’t well-understood by the newer breed of JavaScript developers, then it’s my job as a DOWF (Dull Old Web Fart) to explain what it means, and why it’s important.
Gather round, Fullstack JavaScript Developers – together we’ll make your apps more usable, and my blood pressure lower.

No, really, please read this. I might be biased, I might be a DOWF too, but there's a reason that people who have been accompanying "the web" since the early days keep repeating that the true value and the true fabric of the web lies in its core technologies which are all about meaning, interoperability, and relations.

(…) By choosing the right semantics now, a machine that I don’t know about yet can understand my content and display it in the best way for its users. You are opting out of this if you only use <div> or <span> because, by definition, they have “no special meaning at all” (…)