the "death" of Muni...

I think you are using the wrong definition for MUni. You do not have to be in the mountains to do MUni, just like you don’t have to be in the mountains to do Mountain Biking. It is more a general riding style for anything offroad- all terrain. Just think of the term Mountainbike or All Terrain Bike - MUni is the one wheeled equivalent. So you can be in urban areas while doing MUni!

There are specialised areas of Mountainbiking, most of which have been discussed:
Downhill (DH)
All Mountain (AM)
Freeride/slopestyle
Dirt Jumping (DJ)
Trials
Urban/street
Cross Country (XC)
Short Cross or Speed Cross (SC)

If all of those styles were limited to old men with cars to get to mountains then the sport would not be fun at all- especially since you are not allowed to ride bikes on Mountains around here. On a real Mountain is one of the ultimate offroad experiences but it is definitely not the only way to avoid the road.

I’ve never heard a goat make those sounds- and there are many riders who are much younger. For younger riders money is not as important as having a MUni and lots of free time for MUni.