Лечим Ютуб⁠⁠

Opera - https://addons.opera.com/ru/extensions/details/center-align-youtube/?display=en
Firefox - https://addons.mozilla.org/ru/firefox/addon/youtube-video-center/?src=search
Chrome - https://chrome.google.com/webstore/detail/youtube-options/bdokagampppgbnjfdlkfpphniapiiifn