I never stated modern is by default better. As a matter of fact, I'm the same person saying on our very own forum with kids that are blinded by modern hype that the era of durable components ended at the dawn of the nineties and it's never coming back. But don't mistake quality with durability! I love M730 but it's time is gone and that's why we respect it: it was a landmark in THAT time.
Yes, I have ridden them in most possible situations. By that, I don't mean the Stumpy particularly, because I don't own one, but I used the Stumpy as an example of bikes from that period. The Karakoram is pretty close. The Enduro is an awesome bike, but like most bikes has its flaws. It beats the ass out of a nineties hardtail easily. It's the same weight (depending on what you are comparing it too), it can power up a hill and rip when things go down. I also rode it on the road to trailheads and it's not worse than aforementioned bikes.
I agree that MTBs are way too specialized these days, but that 140-150 mm bike is today's Swiss army that can do almost everything properly.
And that MX obsession? I guess it's the favourite reason for pointing fingers of people who actually have never ridden downhill in their lives. Downhill bikes are a paradox: they are the most expensive out there and still a 400 EUR mid range MTB is better engineered and tested. Because those bikes that sell most need to be bulletproof. If a product manager faults them, the company loses amounts of money. On the other hand, with DH bikes most of the times you pay big money to have the hidden privilege of being an unofficial bike tester as products are rarely dialled. Intense are so smart that they even managed to turn this into a trump! Everybody knows their bikes crack. What to do? Say they're "for racing only" (as if racing doesn't mean heavy duty) and everybody perceives them as Formula One cars that are not to be taken of their track or they'll shatter to pieces. Except that track is maybe the most hardcore place to ride a bike... Hm! All these considered, I'd lie if I said I don't notice a change. Geometries changed for the good (hey, even Giant now has a proper DH bike!) and suspension is coming slowly out of the cheap hype phase. A 2012 bike is most likely better and more fun to ride than one from 2004 or 1999 (yes, I have some of those too). Don't you ride for fun?
Mx