People don't change.
Of course they do. Individually and collectively. You think you're conservative? Go back just 50 years and you're quite progressive. 100? You're left of centre. 200? You're out of your mind on many issues.
Jefferson didn't just want people to be able to amend the constitution (which of course is a good thing to be able to do, and suitably difficult), he was proposing complete re-writes. Constitutional process as they had just done, to reflect the new realities.
Alan you complain that the original framers couldn't have imagined the power of the presidency or the supreme court or the congress - basically, the power of the nation itself. That's entirely correct - they couldn't. The US was dispersed geographically with the fastest method of transport being a horse or a ship, and no means of communications that could exceed that save over a very short distance (signals). The concept of more than a quarter of a billion people being in the same nation. The population of the US in 1776 is estimated at about 2.5 million. The entire world is estimated at a population barely twice that of the US now by itself around 1750. 50 states compared to 13? Australia has just been "discovered" by Cook 6 years earlier and Antarctica just 3 years. The world was hardly known by modern standards.
As James points out, the courts affirm that rights exist when there is an attempt to limit them. They don't create new ones. ALL other rights already exist and are held by the states and the people.