That's very different. Because there are circumstances where not knowing or applying math is a barrier to accomplishing something. Saying "Why should I learn math, I will never use it anyway." means you're banking on the odds that you will never run into those circumstances.
However when it comes to semantic HTML there is no circumstance where you are unable to move forward because you used <div> instead of <figcaption>.
In fact thanks to the sometimes ambiguous descriptions of which semantic tag is appropriate you may find you used the wrong semantic tag which is arguably worse than not using a semantic tag at all.
And at the end of the day after carefully cross referencing and/or memorizing which semantic tag to use throughout your markup zero real world, practical effect has been gained. Only theoretical gains and memorization for memorization's sake.
It sounds like to be save one should only use <div> and <span> tags, style them with CSS and forget about semantics?
It is obvious to me that this is the wrong approach. And I have never said he should use <figcaption> I said he should use appropriate HTML5 tags. If something is obviously a header, use <header> if not, don't. But building everything out of <div>s like it was in his first example code is just making it more difficult to read, there is no gain in just using <div> for everything.
However when it comes to semantic HTML there is no circumstance where you are unable to move forward because you used <div> instead of <figcaption>.
In fact thanks to the sometimes ambiguous descriptions of which semantic tag is appropriate you may find you used the wrong semantic tag which is arguably worse than not using a semantic tag at all.
And at the end of the day after carefully cross referencing and/or memorizing which semantic tag to use throughout your markup zero real world, practical effect has been gained. Only theoretical gains and memorization for memorization's sake.