Sometimes two people just aren't sexually compatible, no matter how much you love one another.

I agree, but I have noticed vast majority of times it all boils down to person being closeminded and not willing to try things.

There are very few people with zero sexual fantasies, most people have some. But they are not always obvious, and only people who regularly try new things discover theirs and eventually become kinky. Kinky is basically equivalent of "I'm open-minded in bed and like trying new stuff, so I can discover what I like most".

Some people use excuse "I'm not kinky" to dismiss new ideas with always the same explanation "I just don't like this/that".

Well, how did they know they are into doggy style? They didn't until they tried.

And most of the times that's the problem. Some people just don't even try.