I recently bought a 2021 Yukon Denali and I trailer a 7 x 14, 5,300lb trailer with 650lb tongue weight. Here's the thread.....
Thought I'd share our first experience towing our 5300lb 7 x 14 dual axle trailer -> camper on a 400 mile round trip over 5800ft mountain and back. We have a 2021 GMC Yukon Denali 6.2L with middle package 22" wheels but no air suspension. Installed a Curt brake controller. Starting with...
www.tahoeyukonforum.com
Using Weight Distribution Hitch - it's been rock solid up to 65mph on freeway. Occasional 70mph passing - no issues.
My experience is the Denali is fine! (Really enjoying it) so it must be you're trailer. In my case, I DIY'ed a cargo trailer and even though the tonque weight is OK and overall weight is well within Yukon specs - I built the trailer with heavy loads on front (kitchen) and rear (garage) and the center is 'light' - which promotes sway!
I'd look to you're trailer loading, tongue weight, and weight distribution hitch for the issue as I'm evidence that a 2021 Yukon can tow very well.