First, you misunderstood the point: the hammer is a poor metaphor because it's something which _hasn't_ changed massively over time – for the 14th century, if you took the ancient Roman who was used to working with these to Home Depot, they'd they'd immediately know what to use work with their modern counterparts:
https://www.britishmuseum.org/collection/object/H_1982-0103-...
https://www.britishmuseum.org/collection/object/H_1956-0403-...
Now, back on topic. Monero's claims have been lightly tested but never against a nation-state level adversary, so I'd be hesitant putting anything onto a blockchain which would be problematic if a flaw is discovered since there is, of course, no way to remove it. That said, let's assume that everything works exactly as planned and they've perfectly nailed the implementation. Do you ever wonder why cryptocurrency people call what they're building cash? That's because while a 14th century treasury officer wouldn't known a thing about hash functions, they were already very familiar with the problems caused by a truly anonymous means of exchanging value: actual cash.
If you've ever read old novels where people had to show explain their source of wealth, maintain accounts at specific banks with good reputations, visiting traders were required to store funds at state sanctioned banks, etc. that's because while it's impossible to tell where someone's coins came from you can make crime, especially tax evasion, considerably harder by requiring people to show positive proof of income and adding points where other people would have to collaborate with you. That certainly doesn't prevent fraud but it can reduce it considerably by increasing the cost and likelihood of being caught.
Obviously we have a big shift in the technology, but that same basic approach works well now: you don't need to control every blockchain transaction if the gateways into the real financial system are required to follow money laundering laws like everyone else. That's one of the reasons why almost no businesses used Tornado Cash, Monero, etc. because they didn't have a need to and when your accountants ask “how will we avoid the drug cartels using us to launder money?” and you say “we can't, that's a feature!”, they're going to start asking questions like who's going to go to prison.