I honestly think it depends on preferance, food species, cultural diferences, and likes/dislikes.
For instance you said ground beef and pineapple don´t go well.
But i could easily give you 2 or 3 recipes with those exact ingredients and they will work spendidly together. The sweet acid from the fruit with the right seasoning on the pork will works wonders. If you go to Taiwan you most likely would find plenty of recipes involving fruit and pork and sweetness fusing with the savory aspects of many dishes.
The problem is that everyone was brough up differently, has different cultural backgrounds and preferences.
For instance a huge number of the worlds population likes cheese....
I hate cheese, i could never eat just a raw cube of cheese unless it was to mix with something or it was some kind of godly cheese that tasted amazing (just an example).
I believe the reason why some things won´t mix well for some people is simply because of preference and and other factors. To be honest food is food and it can all be mixed and eaten together if there is something binding them.
You honestly cant chop a pickle and mix it with raw apple, eat it and hope it tastes good, but im sure some chef out there has made the combination, used certain spices and cooking methods and ate it or served it and it was great or at least decent tasting.
This reminds me way back of a Top Chef Episode, i believe it was season 4.
One of the contestants Richard Blaise, made salmon served with white chocalate wasabi and tapioca pearls. I remember he won that challenge and was praised for the dish. If i was to make it that same dish im sure it would taste awkward, but he made it, he had an idea and concept of how he wanted it done and how he wanted it to taste, and thus it tasted great (at least from the judges point of view).
Food is food, you can mix it, stack it, blend it, sauce it, cook it, etc.... but you need to have a basic idea of how you want the end result to be and how to reach that objetive or else the conclusion can and will be disasterous.
Just so you have an idea right now im working on playing around with a beet and sweet strawberry ice cream, im still thinking on how its gonna be done, but after playing around with it a few times im sure it will be killer.
Food has its complexity and its not just as simple as mixing a few things together with no knowledge of how some of the ingrediants taste and effect the dish that will simply give you an amazing result, experimenting may give you a lucky and tasty end result, but its not so simple as just throwing anything with anything and hoping it works out without having a concept in mind.
I remember a chef of mine told me a story on how when she was working in Italy a few cooks were giving her trouble for being a female cook. Anyway these cooks decided to make barbaque sauce and f*cked it up big time. My chef (a simple cook at the time) had an idea on how to fix the ruined barbeque sauce, no one believed her that it was going to work or be salavaged but she proved them wrong. She made the bbq sauce and fixed it using nothing more then a Coca Cola...
It ended up being some godly bbq sauce.