Well it depends on what software you're talking about. Browsers are way more capable than they were before. I'd be surprised if old computers would be able to play a 1080p video at 60fps even if somehow your network card had the bandwidth for it. And copying/pasting files is certainly way faster than it used to be. Compiling large applications is much faster now when it would be an overnight process decades ago.

Nothing is stopping you from using the old school software but the reality is that old software was missing a lot of the features that we rely on. That's not to say that current software isn't bloated but if you told me I could go back to using the old software I wouldn't (and I could).