Both cars, which I owned, were always in the shop for one broken part or another and under warranty. Maybe things have changed in the past 12 years, but they'd have to have changed quite drastically to get up to par. Then there's the matter of aesthetics... while that is a personal opinion, the current spate of "Lets make the old designs new again" that the American car companies are going through makes me want to barf a little in my mouth. They are huge, ugly, blocky offenses to aesthetic design, devoid of any class or panache what so ever... and the GTR seems to be going down that road, which is a huge disappointment.
Performance wise... maybe the American cars can keep up now adays, but back a few years ago they were just too heavy and unwieldy to compete on anything but straight line acceleration.
I agree with you on the interiors. I've gone through my share of bad interiors... 98-05 Grand Am, Grand Prix, Impala, and Trans Am. My GTO on the other hand has excellent interior and is super comfortable. I've driven up and down the East Coast in it and feel fine the whole drive. However, I can't give too much credit to GM America for that. With the exception of the motor, it is pretty much a Holden design. the car does really really nice around the turns. It's the weight of it that kills you because it destroys brakes.
With all that in mind the newer GM interiors are actually really nice.
The GTR is big and bulky because it creates a very stable platform around the curves. It's interesting how they executed the design. Think about the rally Subarus going to a hatchback style because it created a much more stable better platform.
Straight line acceleration is fun and exciting as well. I know people crack on it, but it's pretty sweet seeing 1000-2000+whp cars fly down a track. Even more so for the one driving it. If a car is lined up against a top fuel dragster, and it gets a 200mph head start, it would lose the race.
You can't take a 2000whp car around the track. Formula One runs about 1000whp and look at their design. When you get into races like LeMans some cars are running around 300whp. Nascar is around 500-600whp. The building of a high horsepower engine with big huge tires on it and a built suspension is a lot more challenging than it seems.
There is the nostalgia effect too. People like it and they are obviously selling. Personally, I hate the new Camaro, but I love the motor. You're right in the sense they are taking steps back in the performance world, but the Corvette is continuing to move forward.