YouTube is a great place to find great content, unfortunately you have to dig to find it. "Surface" YouTube is a terrible cocktail of reaction videos, clickbait, and low effort content.

Luckily I've been able to find a decent number of great channels, so here is my list:

CGP Grey

Probably one of the best YouTube creators around, he makes videos over a broad range of topics.

Baz Battles

Does a great video game like representation of historic battles with tons of background and history mixed in.

engineerguy

Bill Hamock does a great job explaining engineering and technology principals and designs.

kaptainkristian

Pop culture "love letters"

Kurzgesagt

Much like CGP Grey (they do twin videos sometimes), covers a lot of different topics

Lessons from the Screenplay

Discussions about cinema

Lindybeige

Covers topics from dance to military history, but mainly focuses on history

Military History Visualized

Great creator who covers many topics of warfare

NativLang

Videos about language, how they work, and their history

Now You See It

Another channel about cinema

Primitive Technology

A man who never speaks builds the most incredible things out of mud and muscle

Real Engineering

Covers a ton of topics about various engineering topics and issues

The Great War

This is more of a series than a collection of videos, it covers World War I, week by week

The School of Life

Some of their more recent stuff is meh, but their Philosophy, History, and Politics videos are great

Tom Scott

Great videos about things you might not know

Wendover Productions

Videos about engineering topics that changed the world