The creators of SponsorBlock did it again, now we can crowdsource better titles and thumbnails as well. I just tried it with LinusTechTips who is a worst offender when it comes to clickbait and its really great.
Compare without DeArrow
and with the extension
Like the existing "Clickbait Remover" addon, I believe it just removes formatting (caps lock, exclamation marks, other symbols and emojis) of the video title and swaps the custom thumbnail with either a thumbnail of the beginning, middle or end of the video (youtube provides thumbnails for various points in videos).