Utah's in-migration rates are not as bad as you guys are making it out to seem.
https://www.census.gov/data/tables/2...ate-total.html
Open the bottom table here: Estimates of the Annual Rates of the Components of Resident Population Change for the United States, Regions, States, and Puerto Rico: July 1, 2015 to July 1, 2016 (NST-EST2016-06) [<1.0 MB]
Utah had the 10th highest rate of domestic in-migration of any state. It's true that Colorado, Idaho, Oregon, Washington, and Nevada are some of the ones that have higher rates, but 10th out of 50 is hardly some kind of dire situation.
Also, if you want to harp on the Mormon thing, I think I probably know more non-Mormon millennials than Mormon millennials. Of course, my perception is probably colored by living in South Salt Lake and working downtown, I'm sure it's not the case in, say, Utah County. The Mormon Church is losing a LOT of youth, though.
I know a lot of people that have moved here from out of state and love it. I work at a retail location downtown, and a pretty good chunk of the regulars have recently moved here from out of state and usually have good things to say about Utah.
My point is that of course Utah is going to always suffer because of the Mormon thing, whether fair or not. It's always going to be a little bit of its own bubble. But there is more than enough of a non-Mormon, ex-Mormon, out-of-state influence to drive a true cultural transformation of SLC. It's happening already. Look at the reputation Salt Lake has for, say, their microbreweries. There was recently a national article about Salt Lake's surprising coffee scene. Who really cares if most people think SLC is some weird Mormon backwater? The people who pay attention and who care know that's not the case. People here are way too obsessed with Salt Lake City's national perception, and way too convinced that everyone thinks we're a joke.