There are some weird assumptions here, the first being that gentrification is a desirable thing. The process involves driving out all the lower income and working class residents so a bunch of bougey pricks can get a latte without the risk of encountering poor people. Where are all the current residents supposed to go when the already unaffordable housing becomes literally impossible for them to pay for?

Second, Springfield and all the rest of the deindustrialized mill towns in western Mass are basically fine. Things looked (often literally) pretty grim in the last few decades of the 20th century when population numbers plummeted, but they have stabilized quite a bit since then. Most of the blight has been cleared. There are ongoing renovation and community development projects through the gateway cities program and other efforts. While controversial, the MGM alone made a pretty big change to the downtown streetscape. Sorry if downtown still isn't twee and sterile enough to be indistinguishable from a mall food court.

Third, Springfield does not need to exist as a satellite of Boston. It never has. Its insurance industry is more closely tied to Hartford. It functions as an important regional transport hub. Baystate Health provides advanced medical care for all of western Mass. It doesn't need to be closer to any airports. BDL is right down the road. Boston is only the center of the universe for people who live inside the 495.