> many advanced areas of mathematics are inaccessible to most students because no satisfactory exposition exists

What is considered a satisfactory exposition also depends highly on the maturity of the reader. Not in the technical content of a specific area, but in the maturity of their mathematical reading skills needed for that area. This comes up a lot in algebraic geometry, where every student hits a wall when reading the central textbooks. The books are not necessarily hard because the author doesn't have a specialty in teaching and expository writing. Rather, the author is trying to induct the reader into a way of thinking specific to that field and the communication tools they use.

> I hope to see a change in the reward structure and system of values at research-oriented universities so that teaching and expository writing become legitimate as a specialty.

This is a problem in many fields. Teaching and exposition are often seen as low-value distractions from research, the type of work better left to "lesser" scholars (graduate students, non-tenure track faculty). Many mediocre researchers would be stellar teachers but you are more respected (and better paid) for research.

What year was this published? My usual tricks for putting dates on things have failed.