Privacy coins are truly anonymous (especially those that are private by default like Monero and Grin)
No, they aren't. It is near impossible (if not actually impossible) to be anonymous on the internet.
I have nowhere near your amount of knowledge of the mechanics of crypto, but I suspect you're absolutely correct. If someone--like a government agency--wanted to trace any cryptocurrency to whomever they were hunting, I'm fairly sure they could do it.
As of late, crypto has become extremely popular due to the negative effects of COVID-19 in the mainstream economy. People are starting to consider crypto to be a safe-haven against the traditional monetary system empowered by banks worldwide.
I'm not sure that premise is correct, my man. I don't know about what criminals are doing as far as what currency they're using, but the average Joe on the street is using digital currency for sure--but not cryptocurrency. And in the area where I live, using cash to buy stuff at stores and restaurants is now frowned upon unless you have exact change. The US is experiencing a coin shortage for some nebulous reason....but that's beside the point.
I haven't seen any increased adoption of bitcoin or any other crypto because of COVID-19. I'm not sure if other countries are having a difference experience, but I suspect that as long as the banks are still in business people are still using fiat to pay for everything, just like they've always done.
Maybe criminals prefer Fiat because of its high level of adoption in the mainstream world? Or maybe because Fiat has an easier learning curve than crypto?
You're making this way more complicated than it really is. Criminals use cash because criminals have
always used cash. It remains the most anonymous method of payment as long as the transaction isn't done in front of a camera and as long as the currency isn't marked, i.e., by law enforcement in a sting operation.
In addition, cash holds its value quite well, at least in the short term--unlike bitcoin or any of the privacy coins. If you're a criminal who's receiving money for illegal goods or services, do you really want to take on that volatility risk? I seriously doubt it. Anyway, if anyone has proof that criminals are starting to adopt crypto more so than they have, I'd love to see it.