Hi,
The wide, relatively strait (but beautiful) roads and sometimes paths give a sense of movement but not exactly speed. Even when I’m running my socks off, there is a pretty relaxed feel to it all. The cyclists racing by are not helping either 
It would be great to have a couple of narrow, winding cross country and alley tracks that really feel like I’m actually going fast.
I agree. I’ve taken up trail runs in the last year, and would love to see some single track trail runs in Zwift.
I know it’s not a particularly long route, but it is possible to run the Repack Ridge MTB course.
This is a great suggestion. I think a great deal of work needs to be done on the software side for many years to come to make virtual running engaging. There also has to be a change in mindset. Most runners I know want to run short courses, 3 to 5 miles overall, at a regular pace that is natural. They want to be outside in a beautiful park or open spaces or on a college campus. Overall, a home treadmill would be nice to use once to three times per week, but not every day for most recreational runners. The goal is health and fitness for older athletes and not competition. The United States has a very successful competitive running model in junior high school, high school, and college. There are extremely solid training programs through team sports and I have not seen these coaches at all interested in Zwift.