I would argue it's not about being better or worse than another country, but if 1 in 30 drivers have a different understanding then that's a risk. By doing a driving test in the country you live in you gain a greater understanding of what it's like driving in that country.

As a simple example I drove around Northern France and the first day almost went flying off the motorway slip road as I didn't realise how tight they tend to be in France compared to the UK and Ireland.

Exactly. The signs are different, the cultural norms are different, etc. It annoys me that people believe that all Europeans are somehow interchangeable and universal. It does take time to adapt properly.

I almost did the same in France many years ago taking a slip road onto the motorway, almost rolled the car.

I've done a brief Google, and the UK does have one of the hardest driving tests in the world. This matches with anecdotal comparisons with international friends. https://www.zuto.com/blog/driving-tests-around-the-world/

In the UK, driving is on the left, while in much of the world people drive on the right. Arguably it's not so much that the UK is better, but that people should take a test to validate that they can handle the switch. But this would also mean UK drivers should do the same in other countries where they drive on the right.

It’s not especially difficult to swap the side of the road you’re driving on, your brain adjusts very quickly. Millions of truck drivers and tourists do it each year when visiting the UK from mainland Europe and Europe from the UK.