I think it's unfair to suggest that Brexit has produced no advantages. It's ensured the French are now far more dominant in the EU than hitherto, and thus the UK will have to conform to a lot of EU legislation crafted to serve French interests (at least, if anyone wants to attempt to export to the EU or provide services there). It's ensured that Russia can ignore the UK as a potential adversary because a collapsing economy combined with the usual MOD procurement incompetence combined with even less money for the armed forces means that the UK is now a military joke that couldn't even pull off a combined arms exercise in the Baltics back in 2022. Brexit has also enabled other cities to capture a lot of business that used to go to London. It's enabled European nations to capture a lot of trade that the British used to have (98% of Scottish salmon has been replaced by Norwegian salmon, for example).

So, all in all, Brexit has delivered many advantages to many countries around the world. Pretty much the only nation that hasn't benefited from Brexit has been.... the UK itself.

But surely that's a minor quibble?