Hmmm, even though I love Kurzgesagt and this is an informative video. There are easy answers to the questions posed at the start.

How does homeopathy work? It doesn't.
How did it become what it is today? People are easily swindled.
What can modern medicine learn from it? NOTHING.

Yeah, they go on to talk about viewing the patient as a person, etc, but that is not that important. I don't want my doctor sitting down and having a chat with everyone, I want them to treat them and move on to the next patient. Maybe when we get to our AI-led post-scarcity utopia, but right now, medicine (like everything else) is a game of finite resources. Do you really want to waste the time of a highly trained (and highly paid) medical professional? Because while they're talking to you about your vague sense of unease, someone else is dying.

There are some core philosophies withing homeopathy that have some merit for some cases (e.g. treat like from like, stop unhealthy activities to heal...) but it is mostly practiced and promoted by charlatans.

Most of the good ideas that homeopathy came up with were adopted by mainstream medicine anyway.

Yep, as Dara O'Briain points out "herbal medicine has been around for thousands of years.... then we tested it all and the stuff that worked just became MEDICINE"

The core idea behind homeopathy is that water has memory.

So if you put Caffeine in water it "remembers" the Caffeine and when you reduce the amount enough, that causes it to become "negative" which means it'll put you to sleep.

So since all water on Earth has been exposed to other water that was once in contact with every conceivable medication, perhaps we should just drink water instead of paying for some magic water? After all, every bit of water you drink has some molecules that were dinosaur piss once upon a time.

See also: https://videosift.com/video/Homeopathic-A-E-Mitchell-Webb

*debunked

Adding video to channels (Debunked) - requested by Zawash.

Is there some example of where "treat like with like" is useful and insightful? I mean, all I can think of is immunotherapy for allergies.

For a while in history, there have been some doctors who would suggest treating a fever with an icy bath. You know, to bring the fever down. What we know now is that raising the body's temperature actually helps the immune system fight off infections. So, if someone has a fever treating the symptom (hot) with the opposite (cold) is usually terrible idea.

What do we do at home when we have a fever? Warm soup or tea. This makes it easier for the body to keep its temperature up. Treating like with like.