Well, to be fair, ridership for NYCFC in MNR territory is relatively slim. And while it's nice to be able to get there (and not have to play to go from 125th St. to YS- 153rd, regardless of the line you came in on), it's going to be the last demographic the team needs to cater to. That said, building a stadium in the Bronx is going to be the absolute best CFG can do for its fans -- and the most convenient for MNR riders and subway riders alike.Getting to Yankee Stadium by train is not at all convenient for people who live on the New Haven or Harlem lines. So not at all convenient plus a few stops is even more not at all convenient.
This site is less difficult from the East Side of Manhattan than people think. Taking Metro North from Grand Central is just 20 minutes and from Harlem 125th street is just 10.
But, no one's going to want to shell out an extra $13 round-trip to ride it, if they already have a monthly Metrocard. Hell, that's almost the price of admission for most STHs.