I don't think the thumbnails are a terrible idea. When you have a series that has been going on for over 70 videos (Mostly because they insisted on that 15 minute format for way too fucking long), I think it's refreshing to have some different thumbnails. It's helpful when you want to find one specific part of the game, since the titles themselves never helped much. It's just that the execution is awful, and the thumbnails they end up using vary from being dogshit to pure nightmare fuel.
The new titles, on the other hand....
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I kinda love how often the actual name of the game is cut out by those titles, and that's when they don't leave it out entirely.
Imagine being so conceited you actually think your wacky, hilarious clickbait one-liners are more important than letting your audience know what game you're even playing.