LO, those are great points for the limited success of the Dash 7 and the lack of acceptance of STOL transports. I'd add that community opposition to STOLports ("not-in-my-backyard" mentality), the lack of passenger ride quality (as supported by Eastern and American Airlines demonstration flights), as well as the retrictions of a national air space system based on VOR-to-VOR airways, where the MD-188 would have used direct point-to-point routing off the standard airways to minimize route congestion, helped to drag the STOL airline concept down.
Another major downfall of the STOL concept was cruise speed. Over short hauls the STOL transport could compete with the airlines by departing from satellite airports (i.e. small airports nestled around larger airports) allowing passengers to board quicker, aircraft to taxi to General Aviation (light aircraft) runways with minimal delay, and depart direct using the MD-188's Decca RNAV navigational system creating 'ghost stations' (remember this was all before GPS). The STOL airliner would beat the conventional airline in this short haul market. However, over longer hauls the conventional airline would 'out-run' the STOL aircraft due to excessive drag and it's inherent mid-range turboprop performance, which forces the aircraft to lower altitude to maximize its performance.
The STOL passenger transport of the past had a very narrow market. However, NASA, with its higher cruise speed CESTOL design, with quieter and more efficient engines, ADS-B (GPS-based) airspace system for direct routing, may widen STOL passenger transports acceptance and hopefully usage in the future.