People are trying to resolve this problem in a similar way the bitcoin itself functions: https://github.com/bitsquare/bitsquare

That comment is very general though. Exchanging bitcoins for cash, gold, diamonds for example would be harder to trace.

Exchanging BTC for cash, gold or diamonds is much more difficult ( and there's a higher perceived danger ). How would you go about trading your BTC for diamonds?

Btc-to-diamonds.website ? If it's online, it's tracked by 5 eyes Tor? 5-eyes is even more interested Craigslist? Great, go meet a stranger in a parking lot and gamble that you don't get robbed.

The comment is general but it's right. As it & other posters in this thread have pointed out - existing power structures control the world. The internet does not exist in an imaginary "stateless" vacuum.

If you are in the underworld you know people who you can do dealings with. Effectively a dark pool. Dark in both senses of the word.

The average BTC holder is not, so it's not a good option.