The results speak for themselves. The UK government is more based on traditions than a written document. It has lasted since 1688. The US Constitution is mostly written, and it has lasted since 1787. Let's just say that both of these achievements are remarkable in their longetivity. But neither has proven to be superor to the other.

In fact, many South American nations adopted an American-styled version of governance. We would not call these countries as success stories.

So there is more to democracy than a written document--or lack thereof.

Isaac Asimov prophecized the fall of American democracy in his Foundation series. Democracy is not forever.

https://medium.com/tiered-democratic-governance/asimov-foundation-democracy-26ea4578e49d