As a person who loves cities and mixed use activity, Hartford frankly sucks. It has none of the energy that cities that are coming up fast have. (New Haven - for instance; Providence for sure)
Would a $500m Sports centered development change things? I have not seen that the City has any idea how to create the great things that are going on elsewhere or even aligning with groups that do that well. Look at the LWLP program at the old Coliseum site in NH. Transformative. I have little confidence that Hartford will ever pull that together. I see political crap and same ol'. The history across many US cities is about graft & corruption often. The answer is a Residential Walkable city focused on a demand driver like a large medical center (Yale New Haven again) or an urban University. With great dining and entertainment.
If one could role back the clock, Connecticut should have established one major city instead of 3 mid-major cities (Hartford, New Haven, Bridgeport), likely New haven would be it as its centrally located (east west) no too close to one of the borders and can still be linked by rail to New York. The state is too small in terms of populations and resources to support 3 mid-majors and a host of secondary cities (New Britain, New London, Waterbury, Norwalk, Stamford). A 'super' New Haven with East Haven, West Haven, and most of Hamden added to it would have the people and resources to rival Boston and there would be no question on it hosting major sport teams. All well.
New Haven was (and parts still are) a mess in the late 80's and most of the '90s'. The big change happened when Yale realized that it could not live behind its Ivy walls while the city fell apart and expect to survive. Thus, it partnered with New Haven and over the 20 years has truly transformed downtown. Hartford's downfall is that its downtown was built for business and only business so when globalization pulled many of the company's big corporate partners out of the city before the urban trend to pull residential dwelling back into the urban core in the 2000's. Corporations can move with relative ease. Universities can't.
PS - Providence is a lot like New Haven. Really nice downtown and up on Federal Hill and College Hill (Brown); but, parts are a mess, such as the neighborhood around Providence College.