[Too]

Not just any disc brakes, hydraulic ones, at a competitive price and weight. They are so much better than the old caliper brakes it’s silly even comparing them.

Suspension have received lots of improvements, both features such as lock-out, and also generally in terms of better properties, geometries and availability. Especially when looking at the rear frame. Forks are still mostly just forks :)

Finally you also have overall build quality. A mtb from the last decade just feels more rigid and lightweight, you get a sense of confidence the moment you grab the handlebar, whereas 20y ago shifters and handles have that flimsy feeling to it. Warped wheels and flat tires is also much less common problem today.