These SUVs are built with a lot of capabilities. They are comfortable people and stuff movers and they are great at towing. Their very basic 4WD systems are designed with these primary concerns in mind, and they are designed to provide better traction on road under adverse weather conditions and for mild off roading. They are not built with off roading as a primary concern. Have you ever heard of GM even mentioning or promoting anything related to off roading in regard to these vehicles other than slapping a Z71 appearance package badge on them?
I am certainly not an authority on the subject, I just happen to have collected information from off roading for many years, having researched and owned custom builds, and know how many Tahoes I run across on the trail, which is to say almost none, and after extensive research on overland builds I know that practically no overland vehicles are ever built on this platform, both for some of the reasons you mentioned and others.
The whole suspension system, drivetrain, tranny, gearing, hubs, control arms, are not oriented for off roading, they just will not provide the necessary traction, much less articulation, to get out of any serious situation. Not only that but the tolerances of all the components that make up all of those systems are such that they will not take the abuse over the long run, not because they are flawed but just because they aren’t designed for this purpose. A good lift and grippier tires will help a little but have their limits. So you basically have to change everything under the truck to make it seriously capable, essentially having to do all the things that are in that Sportsmobile conversion link I posted earlier. Even Raptors, which are built with off roading as a primary mission require a lot of upgrading of stock components if one is to truly off road them aggressively.
At some point, unless one plans their entire itinerary to avoid places to account for the limitations of their vehicle, one has to have at least a rear locker or an adaptive air suspension such as the ones LR and Jeep use to distribute traction where needed. There are plenty of vehicles in the same price point of a GMT900 or lower with those basics built into them without having to change anything, why start with anything else? For a true overland build, just grab a bone stock used taco/4Runner, FJ, Colorado zr2, or Jeep and go to town without having to rebuild half the vehicle just to get to a decent starting point.
As always everything can be done with enough money. The question here is whether the GMT900 platform is a good one upon which to build an overland rig, and the answer of no is very well established. It’s actually exhausting having to keep arguing something that’s a given by those informed. But with a few mods and some camping gear they will get you out there on the trails and into the wild. The burb HD is actually really good for such things. Truth is about 80% of what’s out there can be handled by a Honda Pilot with a small lift and a/t tires, for most people that’s actually good enough ... very few people actually follow through on a true overland build once they figure out what it truly entails and whether or not they will realistically ever do the overlanding expeditions themselves and need that level of capability out of their vehicle.
And yes there have been epic overlanding journeys achieved by pretty basic vehicles. That's not the point though. Part of ovelanding is not knowing what road conditions are around the next corner, or even if there is a river around the corner instead of a road. It stands to reason that the more tools one has in their toolbox the better their chances of getting through it with their vehicle and themselves unscathed.
