Homebrew not allowing users to install EOL versions of software with no security patches or updates is a _good_ idea. Just because a fraction of a tiny minority needs some ancient version of PHP doesn't make it a good idea.
"pro" users need EOL version support because sometimes some client still didn't want to update his age old web app the newest node or python or whatever. sometimes it's not up to the dev himself, and he needs to make money either way.
so in the end brew makes decisions for the most common denominator, and that will be the user that uses it to install youtube-dl and nothing more.