"People who use the darknet usually are up to no good. This simple realization should be reflected in our legal system."
and
"I understand why the darknet can be useful in autocratic systems. But in a free and open democracy, in my opinion, there is no legitimate use."
It's super difficult to build a low latency mix-net that covertly works inside an adversarial network.
In addition to the current models over which onion/garlic routing are based upon you would (at least) need to add to the core of your software traffic obfuscation, a series of covert channels, NAT bypass, ...
Tor and other mix networks simplify the problem assuming that there's a portion of the Internet that is free and introducing censorship circumvention mechanisms.
Of course, the assumption is increasingly untrue.
If the dark web becomes popular though, won't the same people try to regulate it?
They could make .onion link illegal for ISPs to load and kill it overnight.