Yes, the P4 was a step backwards in terms of microarchitecture. But as I said, now that the ghz wars are over, people are working on improving microarchitectures and that's where performance improvement is focused.
Even if the only thing they were doing was rolling back the P4's braindead design decisions, this would still be true.
That said, this isn't the only thing they're doing and the new Core microarchitectures are really quite an improvement over anything Intel's ever done before. I'm not thrilled with the original Core, but Core 2 on has been an improvement.
I'm not saying it's great, clearly Intel's never going to do cutting edge radical microarchitectures like Tilera, Sun or even IBM (from more radical to least) but you can't possibly claim their newer microarchitectures aren't an improvement that offer tangible benefits to single-core performance.