We had a ‘16 denali xl from brand new to 135k miles, just traded it in on a new rig. Never had any major issues at all. Overall it was a stupendous rig. Great power, plenty of room, and great mpg in my opinion for the size/power of it. The mrc shocks did end going out at around 70k miles, which is actually more miles than most seem to make it. Changed the brakes out at around 120k miles, which were still in decent shape yet. Drivers heated seat went out toward the tail end, as did the AC, which were both fixed by the dealer (at our expense).
In my opinion i would try for a later model year, though, to get the 10 speed trans (think it was late ‘17’s and up). Ours had the 8 speed, which gave us no trouble, but i have read of issues with the early ones with the 8 speed.