I also have a 2015 LTZ with the 10 way power adjustment and hate the drivers seat. It came with factory leather which I removed and replaced with 2016 cloth covers (took 14 hours!), which helped a little, the seams in the side bolsters dug into my thighs. But like a lot of other posters here, I think the foam is way too hard and the seat front doesn't tilt down far enough. I'm 5'11" 180 lbs and a few cheesburgers would probably help.
The other problem is that the pedals are too close to the seat. I have longer legs and a shorter upper body so either my knees are hitting the dash or I'm reaching forward to the steering wheel. It would help a lot if that freaking electrical box isn't where a left food dead pedal should be (I can't believe GM kept it there with this new body style, I hated it with the previous style too).
I've had (no lie) a 1999, 2000, 2002, 2003, 2004, two 2009, a 2010 and a 2013 in addition to this 2015. I don't remember having such a miserable time with the seat in any of them.