I love it when you think of an idea and someone has already made the add-on :-)
My personal bugbear is poor quality crowd shot concert videos that use a thumbnail that makes them look pro shot. This removes that issue, and takes the other clickbaity nonsense with it.

My only suggestion would maybe to (if possible) have the option to exclude/whitelist videos from users you are subscribed to.
Generally if I'm subscribed to someone there isn't really a clickbait issue and usually more often than not thumbnails would be preferable.

ニコ厨必須装備。
YouTuberのアホ面を見なくて済む。スーパーのチラシみたく下品なサムネを一掃し、かつての姿を取り戻せます。
開始数秒後のサムネイルを切り出して、投稿者が付けたサムネイルを上書き可能。

例えば商品レビューを探す時に、目立ちたがりのYouTuberしか写っていないのか、ボイロ等を使った凝った編集の動画なのか、一瞬で見分けが付きます。動画の内容はタイトル文で十分分かる。

スマートフォンでも使えます。YouTubeアプリをアンインストールし、Firefox NightlyとuBlock Origin、本アドオンをインストールすれば、快適なYouTube環境を構築できる。

A must have for todays Youtube.

This is the most user-enhancing extension I have used. I used to systematically block via Blocktube clickbait channels because their bright colours and needless CAPTIALISATION assaulted my mind. It is astounding how lightweight and reliable this extension has been.

works as described , really helpful and truth be told life is a little better without those thumbnails

Hallelujah

I'm not going to use it but for what it is it functions perfectly

Working.

Es una extensión muy necesaria si ves videos en Youtube. Remueve las vista previas personalizadas, haciendo que los videos sean más fácil de distinguir y que el sitio se vea menos tóxico. (Sin mencionar que no vas a ver más gente con la expresión de como si le estuvieran haciendo exploración de cavidad del tracto rectal)

Realmente cambia la experiencia.