You are really delusional. The Brits are soooo class driven it isn’t even funny. If you are not in line you will never be king or queen. If you are not titled you will never be in the house of lords. The class structure in the UK is long and storied. It may have changed a little but it is NOT the US. In the US you can come from nothing and build a financial empire. The only thing stopping you in the US is yourself.
Things are long and storied, but you are more caught up in the story as it was in the past than the reality.
Yes, if you are not in line, a Brit can’t be King in Britain. But you also can’t be King in the U.S. For this particular position, it seems that there is an equal lack of mobility in both societies. The monarch in Britain is also so limited in what he is allowed to do that the position is essentially powerless and more a gilded cage than anything else. I think that there have been some decisions of minor importance made by the British Monarch since, but one of the last was the location of the capital of the province of Canada back in 1857.
As for the lords, Perhaps you haven’t paid attention to how titles are given in the House of Lords. Beginning in 1958, non-hereditary peers began to be the norm, and since 1964, no meaningful hereditary peerage has been created. Since 1999, the number of hereditary peers in parliament has been limited to 92, and they are chosen by and from the much larger group of hereditary peers. The other 683 Lords are peers for life, having been appointed by the government to the house of Lords and not having had titles before their appointment—the best analogy in the American system would be Supreme Court judges, except that the judges are more powerful. In Canada it parallels the Canadian Senate fairly exactly.
Just as nothing is stopping you in the U.S. from becoming a Supreme Court judge other than not having the favour of the President and of the Senate, so in Britain nothing is stopping you from becoming a member of the House of Lords other than not having the favour of the Prime Minister. Indeed, things are slightly more open in some ways in the U.K. because there is no particular customary upper limit on the number of life peers a Prime Minister can create, while in the U.S. custom dictates that someone from the class of Supreme Court Justices must die before you (or some one else) is appointed.
You might also want to check out post 45.