I wonder what the cost analysis was when they compared using the Alpha vs D2xx platform? Seems like it would have been an easy decision to put your Premium crossovers on the Alpha and Omega platforms to compete against your direct rivals and let Buick stay on the D2XX platform and battle Lexus and Acura.
If reports are true, Alpha and Omega are finished; they're not a part of GM's
Flexible Vehicle Set Strategy which is targeted to be in full effect by 2025. See the chart below.
Cadillac somehow seriously misjudged their CUV/SUV vs car mix. Here's my theory as to why the first XT6 is on C1, mimicked the interior of the XT5 and, in many respects, comes across as merely good enough; and why it's continually referred to as a stop-gap product.
By the time Cadillac determined to do something about their dearth of utilities VSS was instituted leaving a relatively small window of time to develop new product on existing platforms that were essentially considered dead to GM (which is reportedly the reason the gen 7, Alpha 2-based Camaro had its plug pulled). In that predicament, Cadillac's quickest and cheapest route to a desperately needed product (that would only see a single generation on a discontinued platform) would have been C1, as opposed to investing far greater time and budget to develop all-new crossovers from Alpha or Omega which also, sadly, have one foot in the grave. I presume that's also why Cadillac chose to Xerox the XT5's interior rather than divert their talent away from the pending VSS products (which notably integrate EVs).
I figure GM is being rather militant with regard to their VSS and has put strict limits on product development that doesn't relate. VSS could possibly also explain the CTS/CT5 and ATS/CT4 commonalities and maybe even some of the friction with Johan. For example, VSS-R is slated to replace Alpha and Omega as well as serve as the corporate RWD platform for cars (and crossovers?), while VSS-S be the corporate SUV platform. The tremendous effort to make Cadillac unique and exceptional with Alpha and Omega will be gone. VSS-R will no doubt be excellent but will Cadillac be afforded an opportunity to infuse their product with their engineering prowess and do something special to set them apart, to make them fundamentally better? Cadillac still has their engines but, alas, they're aiming to go full EV.
Time will tell. But for anyone that thinks this first-gen XT6 indicates Cadillac's ultimate aim or somehow defines their future course, they obviously haven't been paying attention to the obvious.