The UK was, and to some senses still is, a culture that strongly values who your parents are vs what you’ve personally accomplished. The head of state is the child of the previous head of state. The House of Lords is still a thing. Prestige based on family lineage is considered a big deal.

In the US and other parts of Europe it’s very different. People value you a lot more because of what you’ve done vs who you are and, with some exception, nobody cares who your parents were. If you have a rich daddy most people don’t care. If you’re rich because you inherited wealth vs earning it that’s see as “less” than those who are self made. While there are certainly exceptions, most of our richest people are in the self-made category and that’s a source of pride. “The American Dream” while a bit of a glossy story is generally a very real thing.

Passing off wealth and prestige by lineage has long been shown to be a bad idea. The next generation typically just screws it up.

Until the UK truly does away with its still quite hereditary ways and focuses a lot more on valuing individual achievement it will likely only continue to stagnate against other economies that have long since broadly moved on from such archaic mental models.