I went and refamiliarized myself with the <spoiler> tag. It does hide the text within it, however, the difference between <spoiler> and <details> is that <details> does not require the page to be reloaded. As the world moves to more mobile devices and plans that might have data limits, reloading pages is not optimal. Also, long blocks of code are not semantically spoilers. While my site is not the best when it comes to being easy for those using assistive technologies, I do try. So, this is not only a way to keep page loads down to a minimum, it is also more correct to use the proper HTML tag. I created a sample of <details> with <summary> so you can see how they work.

As for other HTML5 elements, I don't see any use for them here either. If we ever get <img>, then <figure> and <figcaption> might be nice. They could also be used around blockquotes, like the one I used below.

It might be a good idea to drop <font> as one day browsers might drop it.

This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

- from MDN <font>

So to wrap up, <details> along with <summary> would hide large blocks of code nicely, is more semantically correct, and does not reload the page to see the large blocks of code as <spoiler> does.