TransferWise are not a bank, they are an Electronic Money Institution. Different kettle of fish. The accounts they give you are virtual accounts, not a real bank account.
TransferWise also have larger profit margins than you think, both explicit and implicit by playing funny games cherry-picking rates etc.
So for both of the above reasons, this is why TransferWise can do what they do about giving people accounts cross-border. A lot (most) of it is legal flexibility, the rest is by eating the costs.
There are very few UK banks left that will give you a true EUR account.
Financial services were not part of the Brexit "deal". Which is why UK peeps can't open bank accounts in Europe and vice-versa, too many unaddressed regulatory issues.
Cross-border card fees may well be a similar kettle of fish to the phone roaming charges, i.e. there was protection under EU, but now the UK is outside of the EU it's dog eat dog.
Its a bit like why Amazon UK stopped accepting Visa for a while. Because post-Brexit Visa hiked their rates mostly just because they could.
I'm afraid that given the hard brexit that the UK government has chosen, the UK is only going to see a lot more of this. Brexit itself was bad enough, a dogged persuit of the hard form is, to put it politely, not exactly helping matters.