My list of recommended Youtube subscriptions, built from over a decade of curation.
No Particular ordering within the categories.
(D) means possibly defunct, hasn’t uploaded in awhile.

A tier educational / edutainment

3Blue1Brown - High level math, explained simply with good animation.
Captain Disillusion - Visual Effect explainers
Everyday Astronauts - Deep dive rocket science explainers (also a mix of news and live streams)
Game Maker’s Toolkit - Video Game design breakdowns
Jay Foreman - Mostly humorous looks at maps, best in video sponsor spots on Youtube
Kurzgesagt - In a Nutshell - Animated with a board science focus
Mark Rober - Engineer tackles interesting projects
Mathologer - Long and novel math explainers
Minute Earth - Ecology focused animation
Minute Physics - Physics focused animation
Numberphile - Math and number based curiosities
PBS Infinite Series (D) - Math
Primer - Simulated economy and behavior
Rare Earth (D, likely to pick up after the pandemic?) - Stories from traveling around the world
SmarterEveryDay - Science meets engineering, often meets highspeed camera
Stand-up Maths - Humorous math
Steve Mould - Everyday life curios phenomena underlined by physics
Technology Connections - Deep dives into non-computer technology in your home
Tom Scott - Interestings things, places, and ideas
Veritasium - General science, slight physics focus
Scott Manley - deep dives into space news, kerbal space program

Good educational edutainment (but not quite A-tier by my personal preference)

Ben Eater - Computing projects made with low level electronic components.
Code Bullet - Coding Projects, often automating video games
Colin Furze - Crazy physical builds by an insane Brit
EngineerGuy (D) - engineering explainers
Jill Bearup - Fight choreography
Jordan Harrod - AI / Machine learning
LeiosOS - Various computer science
Linus Tech Tips - Computer projects and products mostly with a gaming focus
Lock Picking Lawyer - See every lock in existence get easily defeated by an expert
Noclip - Video Game Documentaries
Objectivity - Archived objects from science history
PBS Space Time - Astrophysics
People Make Games - Video Game Documentaries
Periodic Videos - Chemistry, and a deep dive into every element on the periodic table
Practical Engineering - Civil engineering
Primitive Technology (D) - Ancient techniques for building and crafting, relaxing
Scam Nation - Small scale magic tricks
Sebastian Lague - Coding Adventures
Simone Giertz - Previously queen of shitty robots, maker style projects
SingingBanana (D-ish, appears on numberphile mostly now) - Math
Sixty Symbols - Astrophysics explained by professors
Stuff Made Here - Engineering/crafting projects
Think Twice - Math animations
Tom Stanton - 3d printer powered home engineering projects
Vihart - math
vlogbrothers - Mixed in with nerdy vlogs are some gems of thought and introspection on our world
Zee Bashew - Animated D&D spells and more
BrainCraft - Human psychology
Computerphile - Computer Science concepts, explained
SciShow / SciShow Space - Science news

Video Essayists

Errant Signal - video games
Joseph Aderson - video games
Mathewmatosis - video games
Writing On Games - videogames
Every Frame A Painting (D) - movies
The Royal Ocean Film Society - movies
Just Write - movies and literature

Humor

Brian David Gilbert - Surreal skits
Casually Explained - Witty introspection on life
CrackerMilk - Short, weird, to the point
David Mitchell’s Soapbox (D) - British rants
Felix Colgrave - Animation, probably tied to drug use
Joel Haver - skits/animation
videogamedunky - video games