My response was that I disagree with this conclusion that something like "pressure to optimize RAM implies another hardware tradeoff" is the primary thing which will give, not that I'm changing the premise.

Pressure to optimize can more often imply just setting aside work to make the program be nearer to being limited by algorithmic bounds rather than doing what was quickest to implement and not caring about any of it. Having the same amount of time, replacing bloated abstractions with something more lightweight overall usually nets more memory gains than trying to tune something heavy to use less RAM at the expense of more CPU.