It's not my role as a fan to concern myself about their ROI or local zoning laws. What I care about is the success of the team, and lacking a stadium impacts the national perception of the program and our recruiting IMO. Not to mention the fan experience. Dolphin Stadium is a good place to see a Dolphins game, it's not a good college football stadium and no amount of rafters or upgrades or flying cats is going to change that.
Without getting in to the weeds on the stadium bit, all I can say is where there's a will there's a way. If they wanted to get it done, they could. UM has a lot of pull in South Florida, and there are many places where something could be built. The excuses feel a lot like a cheap admin stringing gullible fans along, rather than anything of substance. Can't build it on campus or in the Gables? Fine, find some other location. They HAD a perfectly fine stadium - the OB. When they tore that down, they should have had a backup plan in place. "We're tearing this down but replacing it with XYZ." Instead, they tore it down and left us with nothing but a rental that has never, and will never feel like home.