Well, Augy, if Mano wants to like Korn that's his choice as a free individual and human being, doesn't mean anyone else has to. No doubt he thinks a lot of the stuff we like is crap, or would if he'd ever heard it. I will say this to him though;
If it wasn't for the oldies none of the new bands would be around - they would still be trying to get a sound together. And I bet if you asked any of those new bands they would have influences stretching way back. No decent band forgets its roots or where their music came from. Maybe some of the old stuff has had its time but it still lasted longer than any of the bands you mentioned ever will.
Just because you haven't heard of something doesn't mean it isn't good, it just means you haven't heard of it. Most of the bands today are highly derivative with very little originality. Anyone can do a copy with a slight twist, it's doing something new that's really clever. And none of the bands you mentioned are original, with the possible exception of Slipknot. Even though I like them (yes, that's right, I do like them, try not to die of shock), they are all variations on every band in that genre that has come out in the last few years. They have all jumped on a bandwagon that existed before most of them were even born, and certainly before many of their fans were.
As for catching up, lol, where were you when Rock started? I doubt if any of the new bands will last more than 10 years, if that. Bands survive by changing and adapting over the years, not by doing the same stuff album after album, and not by merely cashing in on the current sound. Any real musician will tell you that. How many of the Nirvana copies are still around? Don't bother thinking about it, the answer is none.
Look a bit deeper into the music you (and I, and everybody else) like so much and appreciate the bands who made it possible for them to exist. You never know, you may even like some of it. Nobody ever got anywhere by narrowing their horizons, their minds or their perspectives, they just became clones.
Another beer please, waiter. And another pizza, they were good. Hold the onions again. And the Korn ;-)