Re:
Purely by chance I still have the Rocky Mountain Blizzard I bought, nearly new, in 96, it fits me to a t and I can't see myself ever parting with it, so smooth and comfortable. And even better since I've ditched the suspension fork (it'd been fitted with a succession of poorly functioning suspension forks over the years - I was never able to get it truly dialed in). I've ridden a few moderns, and I'll admit that 1x drivetrains are a welcome innovation (be better with a single thumbie IMO), and I don't know if it's modern tires or the 29" rims, but they do seem to roll a little better on the trails. Here's the big 'but' though, they don't feel particularly connected to the trail, so they make me a little uncomfortable. On my Rocky, I can tell when I'm pushing too hard, bit of brakes and a foot dab and all is well. On a modern, full squisher, you sit up a tad higher, a combination of the higher BB and the uncompressed suspension, so pretty much every time I've felt the need to 'dab', it was a prelude to an ugly off. I don't race, so don't feel a need to be fast, and TBH, I run out of lungs and skill equally on both 

, so I just stick to riding the bikes I'm more comfortable on. Also, I can now afford the bikes I lusted after in the magazines of my childhood, vintage Merlin, Hei Hei, Ibis, Slingshot, what have you are pretty much all available for the price of a half decent department store modern, and they are fantastic riders.
One caveat, I'd really like to take a framebuilding class someday, I think it would be amazing to ride a bike you built with your own two hands, by definition, it would be a modern though...
Cheers, Ted