There's an extension called "Redirector" which can pretty easily redirect links to Youtube videos to an Invidious instance of your choice instead with a rule like .*youtube.com/watch\?v=(.*) -> https://invidious.flokinet.to/watch?v=$1 (set it to pattern type "regular expression" if you use that one.)
It's strange that the Invidious UI is so much better, but until Google improves their version I feel justified in doing this.