It looks to me that the Uk has done a lot better:

https://ourworldindata.org/grapher/gdp-per-capita-worldbank?...

It's not obvious to me that comparing GDP per capita is a fair comparison when talking about one country with immigration vs one without. A lot of the immigration I believe to be not so skilled. But we needed lower-skill jobs filled too.

its quite complicated and changes over time.

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...