>If you are the only person in the world with the private key to your coins, you are the only person who can move them. Period.
This is completely and utterly irrelevant and has not stopped anyone from performing massive fraud. Just look at the long history of crypto scams. They still happened constantly despite blockchains having that feature. It's just impossible for a blockchain to prevent these frauds. It doesn't matter if you still have all your coins if the value of that coin drops to zero after it's revealed the whole market for that coin is fraudulent, which is exactly what happened this week! And multiple times earlier this year, and multiple times before that! It doesn't matter if it's stored on a DEX either, when you're still stuck with a worthless coin that no one will trade you for! How many shitcoins need to collapse before this is understood? Blockchains do not and will never solve this problem because they create the problem, by design, by allowing anyone to manipulate and dump tokens anywhere they want with no regard for what's fraudulent and what isn't. On a DEX you can't even know if the person on the other end is a real person or not without going outside the chain. I can't believe I'm still talking about this after the long, long string of fraud that's happened over the last 12 years. FTX is not the problem, they are the symptom. The problem is blockchains. They're intentionally built to enable fraud. They have no other purpose, and they aren't even particularly good at that because they stop working when everyone notices the fraud.
I should also mention, your statement isn't even correct! There's a very easy way to get someone else to move their coins for you: threaten them. That's the entire principle that ransomware is built on. It's real easy for criminals and the police and anyone else using the threat of force to get people to give up their coins, blockchains don't prevent that and it's impossible for them to do so because they can't affect anything that happens in the real world outside the chain. I really can't understate this. Blockchains are a fraud. Every claimed authority or security provided by a blockchain is trivially defeated by just routing around it or by gaming the market, which is ridiculously easy for anyone with some cash to throw around because there are no real rules or safeguards. They're probably the worst "invention" that's come out of the tech sector in the last 15 years. I really hope this crash is the end for crypto.