Oh man I've got dozens of them !

Since 2000 ? (Narrow it down a bit)

How about Merchant of doubt - Robert Kenner. Very Very relevant to today !

Man on a wire - James Marsh.
Be advised. This is the story of Phillipe Petit's attempt to walk a high wire between the two Twin towers in New York back in '74.

Into the abyss - Werner Herzog.

Dear Zachary - Kurt Kuenna

Inside job - Charles Ferguson - again, relevant to today.

And one you can watch bits of as and when without losing the thread.
Life in a day - Kevin Mcdonald. Wonderful

There's many about nature that are great, and about music, Long Promised Road about Brian Wilson of the Beach Boys made an impression on me.

I feel triggered just thinking about it. Its the first and last documentary that i've ever watched it was called, Gladiator Days: Anatomy of a Prison Murder. I cried for days i was so traumatized. It was about a racially motivated murder that occured at the Utah State Prison. I just kept thinking about the victim's family about his mother and how she has to relive this moment of her son's brutal murder.

Spike Lee’s "4 Little Girls" (1997) about the 1963 church bombing in Birmingham that took the lives of four children. I remember being told about it by family, but this is the story in chilling detail. That kind of cruelty is still unfathomable to me.😞

Tough one, but My Octopus Teacher comes to mind right away. The Biggest Little Farm, too.

Bundy

Ken Burns the History of Baseball thought I knew lots but it proved me wrong in a good way!

Would be impossible to choose most interesting but a Norwegian documentary I recently watched, “The Remarkable Life of Ibelin” was very special and unique.

Hmm.. IDK, I could not choose just one, the list is so long as it's a favorite genre of mine. I'd have to think about it.

Hitler

Not sure if it really counts as a documentary, but Albert Bartlett's lecture on exponential growth came to mind immediately.

The newer one about the doctor/trainer for the Ohio State wrestling team. It made me disgusted at the society we live in today.

I watched a lot of them.. they are all interesting imo

Recently, it was the Jury: Murder Trial. Not exactly a documentary but really interesting all the same.

Off the top of my head I'll say Children Underground

The Trial of Lee Harvey Oswald. Can't forget it.

Engineering disasters.
Drain the oceans.
How it's made.
Life after people.
Anatomy of a disaster.

Architects of Denial.
Disturbing, horrific, sad, but informative.

John Olinger Does the Kardashians in a Hot Air Balloon

Kumarè.

Yo mama 🤣