So the guy who made SponsorBlock made an extension to crowdsource thumbnails and titles. It's actually fucking great. It's refreshing to see actually descriptive titles and stuff. For anything that doesn't have crowdsourced information it'll pick a random screenshot from the video and format the title to remove excessive caps and punctuation.

https://github.com/ajayyy/DeArrow
https://addons.mozilla.org/en-US/firefox/addon/dearrow/

Some examples:

Before: The Most Misunderstood Concept in Physics (Veritasium)
After: Energy & Entropy: Explained (DeArrow)

Before: The Most Dangerous Weapon Is Not Nuclear (Kurzgesagt)
After: The Double-edged Sword of Bio Engineering Research

Before: You'll regret spamming me... (Linus Tech Tips)
After: Viture 1 AR Glasses Review (DeArrow)

Before: I Paid A Real Assassin To Try To Kill Me (Mr. Beast)
After: I Asked a Former Military Assassin to Try and Steal a Backpack from Me That Contains $100K (DeArrow)

Before: Bullets HITTING Bullets in Slow Motion - THE IMPOSSIBLE SHOT - Smarter Every Day 287 (Smarter Every Day)
After: Firing Two Bullets at Each Other in Slow Motion (DeArrow)

Before: The sad truth about Twitter’s rate limit (Fireship)
After: Speculating on Why Twitter Added a Ratelimit (DeArrow)

Before: I asked President Obama if he's DEPRESSED!? (Hasan Minhaj)
After: Interview with Barack Obama (DeArrow)