Wise used to be almost completely free (excl spread), but they also introduced small % based fees over 1-2 yrs ago. They have had and continue to have many competitors, all of whom are experimenting with pricing models all the time.
If crypto could solve this, or if a trad-fi competitor could disrupt this, they would have. But that is not a very satisfying story, so here we are…
One is of course always free to use real cryptocurrency too, e.g. BTC and XMR, although they are subject to pumps and dumps, although the price rises over time.
One does not “solve” forex by trading in a common shared currency, that is already possible without stablecoins - it’s just that vendors often want their local currency and therein lies the problem.
Even if everyone moved to stable coins or Monopoly money, once you need to cash out in IRL, you encounter forex fees.
A sort-of example is Trump’s insistence on oil being traded purely in USD for the USA’s hegemonic benefit - but other nations are waking up and opposing this status quo actively.
I strongly suspect the reason is the regulations themselves. KYC implementations cost money, and so do fraud disputes. Traditional crypto provides neither, so the fees ther are much lower.