Old Britain would have modernized its industry and either held on to some of its colonies or ended up running Europe, but New Britain didn’t have that kind of energy.
If your old and new bracket the World Wars, I expect you are right. The 20th century largely sapped the life out of Britain and much of Europe.
Still, I was thinking, the other day, that in the days of sailing ships, England could be, and was, a mighty power. Once rule of the seas shifted to using natural resources from within your own land, I expect England’s heyday was largely over.