The Suburban is a mechanically bullet-proof vehicle, without question, and I love them. I drive them at work, I rent them when I head back to the States for vacations and when I'm in the market for another vehicle in 2 years time, the Yukon XL is the only vehicle on my list. With the exception of the GMT800s in terms of styling, I have yet to dislike any generation of Suburban.
That being said, build quality in the past has left a lot to be desired. Even on the GMT900s built between '07-'14, you had cracking dashboards for instance, which was very common on all the Caprices and Parisiennes we had in the family back in the 1980s; right there with sunvisors dropping down, interior and outside door handles that would snap off among other things. You would think this would be something they addressed in two decades. Cost cutting is always an issue, and it's not just a GM thing; I've noticed thinner carpets, for example, across the industry, not just GM products. But flaws like cracking dashboards should not be an issue in this day and age.
GM has not been a market leader in build quality for a very long time, unfortunately. They have, however, been stellar when it comes to drivetrains; particularly their V8s. The GMT K2XX vehicles built between '15-'20 have definitely been an improvement compared to the GMT900 in all aspects - softer, better quality interior materials are particularly noticeable. Now it looks like they have taken it up a couple notches with the GMT1YC.