This isn't the case. The stuff you read about this is just ludicrously inaccurate.

One, UK is growing at about the same rate as other developed economies. This is quite remarkable because, if you look at Europe, 100% of these countries have significantly higher unemployment.

Two, productivity growth has slowed everywhere after 2007. The UK is comparable to Western Europe, slower than Germany, faster than Italy, it depends heavily on what start and end date you pick. This isn't particularly surprising given that we essentially outlawed the most productive sector of our economy after 2007.

Three, the UK had no financial boom in the 2010s, the US did, and the EU did...let's just wait until the debt has to be repaid to see the full score on whether that has worked out economically.

The culture in the UK is to live for the weekend. Weekend consisting of getting drunk and watching football. A lot of the people carrying it both in blue collar and white collar jobs are foreigners. Even when it comes to academics, go to any top university and you will forget you are in the UK.

As well as declining productivity per worker, they are also suffering a declining worker pool as more people are switching to part time, taking early retirement, or are claiming unemployment/disability.