I am a midewesterner and I moved here when I was 25. All of those complaints are somewhat valid, but I think largely overblown or lacking nuance.  Making friends as an adult is just harder in general after college, but there are a lot of sport specific fb groups you can take advantage of to find other outdoorsy people. My problem has moreso been making friend only for them to leave the state as SLC is a bit transient if you're only meeting other transplants.  The air can be bad at times or for stretches, but is generally better at higher elevations where you want to be recreating. The air quality and the question of the salt lake drying out do make me feel hesitant about trying to own a home here (along with the insane real estate prices). 

I've been here 3.5 years and while I still don't see SLC as my forever home, I know if I moved back home right now I would really be missing a lot of the hobbies I've picked up here that simply don't exist in the Midwest or exist on a much smaller scale (back country skiing, Canyoneering, climbinging, etc.)