A Mix of Brexit, an aging population, massive underinvestment in basically everything, covid mishandling and huge debt means the UK is around year 0 of a lost decade. I will leave if I can.
I think we are heading for a tipping point. Public services are probably already past a point where staff quitting is piling more work on those left, resulting in more people quitting. I suspect there will be a terminal snowball which guts the NHS at least and leaves it unable to function (by design of the Tories, of course).
I suspect the brain drain will be similar. Young people don't want to live in some tax haven, they want a country that functions. Brexit has made it harder, but people will find a way eventually. People were talking Canada, the Netherlands, etc... (Notably for here, very much not the US which is seen as having all of the same problems the UK has).