I've found that the best explanation of what we really lost is in some of the comments by Kent Pitman in some comp.lang.lisp discussions, like this one: [1] and

I've found that the best explanation of what we really lost is in some of the comments by Kent Pitman in some comp.lang.lisp discussions, like this one: [1] and this one [2] [1] https://groups.google.com/g/comp.lang.lisp/c/QzKZCbf-S6g/m/KnsOdcyWzc8J https://groups.google.com/g/comp.lang.lisp/c/QzKZCbf-S6g/m/K... [2] https://groups.google.com/g/comp.lang.lisp/c/XpvUwF2xKbk/m/o6CKxgzNLFUJ https://groups.google.com/g/comp.lang.lisp/c/XpvUwF2xKbk/m/o...