I guess I'm sort of confused how the Gillette area would blossom with TOD if only they had trains every 30 minutes...it's still 23 miles to Boston and, more importantly, they'd still need a ton of parking because people go there from all over New England to get to games, not just along the Franklin Line. And structured parking is obviously significantly more expensive than surface lots.
Many of these people are wealthy and drive in from low-density areas, including New Hampshire and Maine; they're not going to go into Boston / PVD / rte 128 and then take a train out. Kind of the same reason Logan only has a ~13% transit access modeshare, with the majority of that on express buses and not the BL / SL -- people are coming from far out and they skew wealthy.
Maybe there would be some residential by the train station with good service, like there is at Mansfield or Canton but I strongly doubt we'd ever get real urbanity there -- it's going to have a sea of parking forever.
That is true but relieving traffic congestion is non linear such that even if we get 10-25% to take the train, the traffic situation will ease up. And of course if the CR were a connected regional rail network with NSRL that gives a lot more suburb-to-suburb 2-seat rides with travel times that would still be faster than driving.
That airport stat is a bit depressing for an airport that is so close to the downtown core (and effectively in an urban environment). I got to think if the transit options didn't suck so much (i.e. have a people mover to the blue line, or silver line doing 3 laps of the seaport before actually reaching SS where everyone is trying to go) it would be greater utilized. You're probably right that the users here might skew wealthy, but I'd imagine majority are still within the Boston metro area (i.e. within reach of the MBTA heavy rail & bus). Of course, many of those on the outskirts (Newton, Quincy, Sommerville, Revere) are opting to drive because having to make 1-2 transfers makes the trip woefully uncompetitive with driving. But if the transit options were better they might be willing to switch modes.