Scott, your observations are right on target. It is extremely hard to create new options outside of the clusters of ride options which occur naturally.
Social groups drift over time toward two poles. In our case, the popular rides may be described as “long and fast” and “short and slower.” It’s hard to create new rides in between even if there are riders who would like to try “long and slow” or “short and fast.”
After I learned this lesson from VBC, I realized we had the same issue within another VBC, namely the Vancouver Bridge Club. Our daily duplicate bridge games are mostly “long and fast-paced” or “short and slower” even though I’ve repeatedly tried as bridge club president to create options in between.
It’s just the natural behavior of social groups. I applaud you and the ride leaders for keeping it vibrant.