This is a common fallacy when it comes to inventions.
I have a Ph.D. in an engineering field, so I'm not easily impressed. That said, the inventions which are truly revolutionary are the ones where as soon as someone describes it you think "man, that makes perfect sense".
Yes, it makes perfect sense because it's the correct solution. That doesn't make it obvious before someone came along and spelled it out, nor guarantee that someone else would have invented it earlier.
There are some types of inventions "whose time has come". These will get invented at around a particular time by virtue of the supporting technology existing. Take the brightness control of LEDs using PWM and color mixing of different LED colors to make color changing LED lighting. Philips actually has a patent on this, from 1999. It was an idea whose time had come, and others came up with it independently many times since and frankly probably quite a few times before. But it was inevitable. I think it was a bad patent because it was obvious even in 1999 that you could use PWM, common already, to vary power through a LED to control brightness. It was also obvious in 1999 that you could mix two different primary colors together to form a mixed color. Patents aren't supposed to be awarded by simply taking two already obvious things and adding them together (or at least so says my patent attorney, who is perhaps too ethical about what she'll let me put into an application). But besides all that, I would argue that any "idea whose time has come" is probably also inherently obvious to someone skilled in the art at the time of interest.
On the other hand, there are some ideas which are not limited by any technology; they are limited by the creativity of humans. Take for instance the liquid metal battery that my employer works on. You float a molten anode metal on a slightly denser molten salt electrolyte on a slightly denser molten cathode metal, and bam, super high energy density, super high power density, low cost, long life-time battery. This is, in my opinion, an actual invention. There was nothing stopping someone from coming up with it earlier... but no one did. Why? Because it was non-obvious. It's still simple, conceptually at least.
As far as pinching to zoom? Honestly, I think it's somewhere between these things. Just because it's intuitive doesn't mean it's obvious. It's clearly more of a jump from a zoom button to a multitouch gesture than the jump from "LEDs can have variable brightness and different colors" to "LEDs can be mixed to make color changing lights". But it's also probably an idea whose time had come, by virtue of multitouch starting to exist. But I doubt any of that had anything to do with why it was invalidated; my guess would be that it was invalidated because of sufficient prior art to render it an obvious extension of existing technology.