that the conditions extant when we were all at that stage in our lives (for me, that was twenty years ago) are not the conditions extant for the people that are at that stage in their life right now.

Yes, there is a tiny group of people that float from the bottom to the top, but the simple truth is that the US is pretty much the most class static country in the OECD, and has been for a long time... and is getting more so, not less.