None of what you describe is unique to Cadillac -- this is what it is to own a luxury automobile. If it is not worth the price, don't buy one.
Which may be one reason why Lexus unexpectedly has a good total cost of ownership.
BTW, the Lexii had far fewer squeaks and rattles after 6 years than the Cadillac did, and had a much quieter ride overall.
As another commenter pointed out, this is quite common on performance and luxury vehicles because it has handling advantages. If you're buying a luxury car, you're by definition choosing to pay more than is absolutely necessary for (what you consider to be) a better experience. The tires are part of that. You can argue that the line should be drawn elsewhere, but it's not arbitrary, and it's very much in line with the market segment they're going after.
It's a SUV. They get used to tow boats, take science-fair projects to school, and take the family on vacations. They aren't used for track days at Road Atlanta.
Performance vehicles I disagree. Handling choices are up to the mechanic/driver and you want to give them options but also make their maintenance choices simple. You should have a wide range of tire options on a performance car.
Repair costs like that adds up quickly. Like the $1200 3rd row seat motor that died. She started calling it the thousand-dollar-car, since any repairs were around that price.