And while I certainly think it's fair to describe the UK economy as a sinking ship, I also think that blaming that on Brexit is, to put it politely, "starting with your conclusion". UK growth has been higher than France, Germany or Italy since 2016. Brexit has obviously had impacts, but they haven't all been negative (the City in particular has zero enthusiasm to fall back into any EU alignment) and I think the COVID lockdown shambles and the Homerically inept current government have been bigger factors.
I found this a decent recent overview on the common analytical takes, if you're interested: https://julianhjessop.substack.com/p/what-the-nber-gets-wron...