I always argue that the demographics have changed because it's what the manufacturers are producing. We can't buy cars from Ford anymore because Ford doesn't make cars anymore. For example, my wife and I would have happily purchased another Taurus after the last one was totaled, but it's no longer available. Instead, we got a Hyundai Tucson. We looked at the 2015 - 2019 Explorers, but she said it was too big for her, so the Hyundai won.
I look at it like this: many people today who are our age 20 years ago are barely interested in cars at all. They're a better match for the automated appliances on wheels, vehicle-as-a-service snake oil of Tesla. There's definitely been a demographic shift. As older car enthusiasts stop driving, they're not getting replaced by new drivers who want the same thing.
Our tastes are less likely to change and are probably fundamentally the same as they used to be, and we should be better off now than we were when we were younger. Theoretically, we should be able to afford to drop $80K on a Dark Horse. Not all of us want one (or any Mustang) though.
My opinion is that Ford abandoned cars because they weren't willing or capable of building a solid (define that how you want) car that touched on what people who still wanted Ford cars liked about them. I'm not sure what the hell that is, but Chevy's going through the same thing. Maybe decades of cost-cutting doesn't help your reputation when Honda and Toyota are out there and even shitbox Nissan Altimas are perceived as better.
Then if you want the upscale experience that our older selves may want or afford, you look to Germany. Lincoln was dead after the Town Car which was propped up by livery services. Probably even before that because they had no successor planned to even keep that market. At least Cadillac had plans and leveraged the Corvette and Camaro engineering teams' work.
If you ask me, I'd probably say that Ford lost me after their last chance at a respectable sedan, the Taurus, ended up having the dimensions of a whale and the interior room of something much smaller than that. This is no joke—I completely wrote off the fourth gen SHO because I couldn't stack it and the Thunderbird on my lift. Realistically though, how seriously was I considering one? Not very. It was a distant fifth on my list up until that point. It failed at all the things that made the third gen SHO a cult classic, and we know that had nothing to do with looking like a jellybean.
In reality though, Ford lost me after the Terminator Cobra because the only sedans I wanted from them were made in Australia. But even then, I would have only counted as one potential customer.