Kinda late to the party here but I’ll share a couple of my favorites:
Melodysheep - video essays about science and science fiction with absurdly high quality animations and production value
Mustard - same as above, except about interesting and/or unusual real vehicles
Casually Explained - just a dude with a great sense of humor and crude artwork explaining random things to you
Sam O’Nella Academy - same as above, except covering very specific and much weirder topics
Biblaridion - his usual content is about conlangs (don’t ask, I don’t know either) but his ongoing Alien Biospheres series about speculative evolution is simply amazing
TierZoo - highly entertaining videos about animals and zoology, except it’s all a videogame
LowSpecGamer - as the name implies, he used to make videos about making AAA games run on potato systems but has since pivoted into making (great) mini docs about the history of videogames and technology
Cyriak - he doesn’t post often but the dude has been making the same kind of technically impressive and often disturbing animations for over 15 years now