Unfortunately, its not an entirely wrong train of thought.
Who needs to buy things anonymously? People buying drugs or weapons on the darknet.
Most average people will just pay for things with a credit card.
Until you give people the ease of use that a nice GUI, the ability to change fiat back and forth to a currency, and things like this,
you have to think- what are the reasons people will use this currency?
For now Monero, and even Bitcoin, haven't given us much reason to adopt them other than to invest, sit on your coins, and hope they accumulate value.
How about a big business wanting to buy anonymously as to not let their competitors know where they're buying from?
Or how about anonymous donations to political causes/parties or even charity? Or someone who wants to avoid having their credit card info floating around on the internet? Or someone who just simply enjoys privacy without necessarily doing anything illegal? Or someone who wants to store their money outside of traditional storage because of the uncertainty of the times (and what added bonus isn't anonymity?)?
The list goes on and on if you just put your mind to it. Of course, drugs and guns and rock n' roll will also easily fit into that list. However, there's more than
just privacy in XMR; there's also all the 'conventional' arguements from bitcoin (cut the middle-men, trustless system, take money printing away from the state, etc.).
In the end, there's also the fact that fiat currency is currently #1 in criminal transactions. It was never about giving anyone something 'new'; cash already does what XMR does, minus the 'sending from anywhere to anywhere' aspect. It's not going to be fundamental whether or not the money used is anonymous; criminals will
always find a way to do illegal things. Until cash is banned by our Google overlords, XMR will not be the driving factor of any criminal network. (And if it is the driving factor, the network will always want to transfer XMR -> cash)