You can create a park out of land that was once not a park. Check out Fresh Kills Park in New York, that is sitting on top of a landfill.What people now view as 'parkland' is really just overgrown industrial wastelands filled with weeds.
Maybe grass and trees don't excite you much, but many of us feel they are an important part of our environment. The Kenilworth corridor is a valuable example of rehabilitated parkland. But I get that it is a matter of how the region values the corridor when weighed against the convenience of the estimated 30k riders.
Imagine we were discussing putting in a new BRT transit-way that goes from the West Lake station area to 394 via the corridor. That would sound crazy, and it would be crazy. But because this is a train it gets some kind of magic bonus points in people's minds.