Shit? Illegal? It's literally your right on videos like <https://www.youtube.com/watch?v=JSEJApMIrLU>. Expand the description and see at the bottom: license is set to creative commons. The copyright holder permits everyone to remix the video but youtube still does not show a button for you to actually make use of that

You need to breach the terms of service (use a downloader) to exercise the rights of the content license that youtube supports