Cure worse than the disease. A aging population is economically ruinous.
Post Brexit changes make it easier for high skilled workers and harder for low skilled. I have not idea how big the actual change has been.
There have been other events and rule changes that have had an impact - covid and Ukrainian visas.
Some interesting data here: https://migrationobservatory.ox.ac.uk/resources/briefings/mi...
https://ourworldindata.org/grapher/gdp-per-capita-worldbank?...