I tend to agree. Back in the day, the performance was really conservative in stock hardware and the stock cooling was generally small.
People couple actually go mad with adding cooling to get their machine quieter or cooler and push the hardware further.

I think now, the hardware is released with a lot less headroom so the gains aren't as exciting as they used to be.
I was never a super super OCer, but always squeezed what i could reasonably. It used to be that I could get 10-30% extra from my kit. But now it almost feels like there's barely 10-15% to be had.