A core i7 is a modern technology and pretty much in its own class . Its the exception not the rule; and pretty much all of there previous processors followed this rule. And of course there's more to it than that. ISA, ALU counts, Pipeline width, pipeline complexity, software, etc.
No it isn't an exception. That it's higher clocked and faster per clock than the comparable weak competition, doesn't change the fact that higher IPC works against high clock.
You can even see this by looking at Intel - even by now no Intel cpu has ever reached the clock of the P4.