What process should be used to decide which are these modern human principles that are too important to be left to majority rule, and who gets to participate in that process?
Yes, the majority has often wanted to do things we now think were reprehensible, and this is certainly an ongoing situation. But Churchill is still right: democracy is a terrible form of government, it's just that it's not quite as terrible as every other form we've tried.
And you haven't answered my question - what should we replace democracy with, and precisely how would that process work - and without answering that question it's tedious to make pronouncements about how much better some undefined alternative would be. G.K. Chesterton: "Revolutionaries are always right about what is wrong, and they are usually wrong about what is right." It's easy to see the flaws in something that exists in front of us. It's very hard to design something that would in actual fact be better.