210cm straight skis from 1985 still "work" but there have been huge improvements. Same with bikes. Not to mention ridiculous weight differences.
My Joshua Z1 is full-suspension and I still have the ad from where I bought it that says 24.5 lbs - it's heavier now due to liners in tires and not always replacing parts with lightest version.
Newer full-suspension bikes tend to be heavier, most are in 28-32 lb. range, although you can spend a lot to get a little lighter. I realize that newer bikes also have suspension with more travel that works better, bigger (both diameter and width) tires and even lower end models have disc brakes that work better, but also are heavier and prone to new set of problems.
This is a familiar pattern. You are in the (understandable) clinging / rationalizing phase. If you went out and did a whole multi-hour ride on a contemporary high-quality FS bike that was set up correctly for you, every subsequent ride on your Joshua would likely be profoundly frustrating, weight savings or no weight savings. At some level you probably know this. That's fine. A new bike is very expensive. Most of us can't just go out and pick one up without a lot of financial planning ahead of time. But that reality doesn't make it accurate to say that a 1997 FS bike has any meaningful performance or function advantages over a 2015 FS bike, any more than a 1997 "shaped ski" has advantages over a 2015 shaped ski. If the newer bikes are heavier, it's because the weight adds so much value that it's worth it to the vast majority of riders. And those for whom it's NOT worth it are all on hard tails, which can be REALLY light.