The Cadillac naming system really isn't any more confusing that any other line. The ATS isn't a cheap Caddy, it's a smaller one. The CTS is midsize, and the XTS is the new name for the flagship (they dropped the STS and the DTS). If you look at BMW, they've always had the 3 Series, the 5 series, and the 7 series. That's small, mid, and large. In America, small has meant cheap or entry level, but the BMW 3 series is the most desirable to many BMW fans. This idea is evolving here too; now you can get a small hatchback with leather, Navigation, back up cameras, self-parking, etc. from Ford or Chevy. And you can pay $30,000 for it!
Now look at the complete list of BMWs, you've got the 1 series, the 2 series, the 3 series, the 4 series, the 5 series, the 6 series, the 7 series, and wait for it - the 8 series. They change the name for every nuance; different engine - different model name; coupe instead of sedan - different model name; convertible - different model name; add turbo - different model name.
And Ford? Ford currently has the Fiesta, the Focus, the Fusion, the Mustang, and the Taurus. And who can forget the Escort, the 500, the Probe, the Tempo, the Contour, the Thunderbird, the LTD, the Crown Vic. Or the older models, the Fairmont, the Fairlane, the Maverick, the Mustang II.... Those are just the one's off they top of my head; I'm probably missing several. Plus you can get Mercury versions of all of those, and if you find a similar one in Australia or Europe - well, it's got a different name. Unless it the "world" version, same name but you can get it with a diesel engine.
As far as the current Caddy lineup, I really wouldn't compare an XTS to anything Cadilac made in the early nineties. Hell, that's over 20 years ago! They've won several awards and car magazine reviews in the past several years. They're not for me - but neither is Mercedes, Chevy, Honda, etc. I like Fords, Nissans, and BMWs. Personal tastes and experiences. If you like the Caddy, get a warranty and drive the hell out of it. From what I've read, they're built for it.