If you can't stand the horrible thumbnails people use on their YouTube videos to grab your attention, the DeArrow browser extension is for you. It's an "open source browser extension for crowdsourcing better titles and thumbnails on YouTube. The goal is to make titles accurate and reduce sensationalism. No more arrows, ridiculous faces, and no more clickbait."
DeArrow replaces thumbnail images and titles with crowdsourced versions. You can also change titles from title case to sentence case.
My daughter said she doesn't like this plug-in because it makes it harder to tell which videos suck. She's got a point!
Here's a video that DeArrow creator Ajay Ramachandran made that explains what it does and how to use it: