A protagonist's intelligence is limited to that of the author?

Semi-true.
It depends ob the type of intelligence that the author wants to show.
Split second decisions, intuitivel knowing something or quick wit are easier to do than some scheming, strategic thing.
Simply because rhe author has longer to think about it than character, so as long as they put the thought in, they can come up with something.
But strategy and schemes directly rely on the authors ideas no matter what 

I'd attribute it all to the type of story that is being written.  Sometimes you do not need intelligent characters.

And intelligence isn't a always a driving factor for certain genre of stories. Romance & Drama are one such story. 

An argument can be made that the author can bypass the intelligence needed to make intricate schemes if they have read enough stories. Just find schemes that were not simple but also not convoluted in the stories they read and alter them enough to fit their story. or they can simply use them as something to base off of. neither choice needs high intelligence just enough creativity to make it work. 

Not really. You don't need to be top world genius to write about the top world genius protagonist. It's about how you make the MC felt smart to the readers.

Although the quality of the story is tied to the Author's skill and intellect, it's not the sole deciding factor. 

That’s why very few fiction novels can have characters considered uniquely intelligent or have unique strategies in the sense that “Oh I never saw that coming from the mc”. Usually I can guess almost every scenario for what the mc will do next. 

*agrees* yeah.. its mostly correct... how can they write something they dont really know... even if they look it up on the internet, its not like they can fully understand some intellectual things..
well, just mostly coz sometimes authors based their characters on real people too no? and if by some lucky coincidence, the referrence of that smart mc is his/her friend, then i think there's a chance for the author to not be limited by his/her own intellect... 

Well the closest thing to intelligence is the appearances of it.

That's why authors usually base their writings on something that already happened and retell the story in an abstract way. Like how the yellow brick road was based on politics.

Protagonist intelligence is not the only parameter that would define how smart a novel is.... 

I'm going to agree that it's very hard to write a character smarter than you are.  Now it's always possible to create a character who is capable of making all sorts of wondrous items or technologies, but this isn't really intelligence.  It's just a nebulous superpower hiding in the guise of intelligence.  What is intelligence are qualities like the ability to come up with plans, to be able to figure out insights based on incomplete information, or the ability to come up with seat of the pants quick thinking.  It's possible to fake these to a degree, but if a writer isn't intelligent enough or at least not well read enough, it'll never come across in a convincing manner.