Is it possible to be able to withstand intense flavors while preserving sensibility to subtle ones?

It's probably true that tolerance for extremes of a specific flavor or sensation will be associated with less perception of slight amounts of that same thing.

So for example, if someone can tolerate extremely hot peppers, they're unlikely to notice a very small amount of heat. It doesn't even have to be extreme: it's quite common for someone with a decent tolerance to not notice that food is hot, while someone else with low tolerance will think it's hot. Similarly, if someone is somehow not sensitive to acidity at all and can drink lemon juice, well, they don't can't perceive that taste so they probably won't notice a tiny bit of citric acid added to water.

But none of that means they'll be unable to perceive different flavors. Black pepper is a different flavor from a hot pepper, so someone with tolerance for extreme heat can most likely still taste black pepper. Someone with tolerance for extreme acidity might not taste the sourness of a little lemon in water, but they could probably notice the fragrance. Someone with tolerance for hard alcohol might not as easily notice the alcohol content of cider, but they'll certainly be able to taste the sweetness, carbonation, and apple that differentiate it from water.

You seem to also be interested in someone having extreme tolerance for everything. First off, keep in mind that there are two parts of perceiving flavor: taste and smell.

Your tongue perceives a small number of basic tastes, most of which it's easy to overdo, like the heat and sour you mentioned, or bitter or salty. For those, if someone has an extreme tolerance, they are likely to be less discerning about smaller amounts. Sweet is probably an exception; everyone can eat pure sugar, and also taste hints of sweetness. Bitter is also a bit unique in that there are a wide variety of bitter-tasting chemicals, and people can have different sensitivities to different ones.

Most of what actually makes foods unique is the more diverse things your nose senses. For most of those, it's not really realistic to ever encounter extremely intense versions. But generally I would expect that yes, if for example you can smell orange extract and hardly smell anything, then you definitely won't notice a hint of orange. Note that this is not about withstanding intense flavors, though, but rather about not really perceiving the flavor in the first place. If on the other hand, it's just that you tolerate it, that might just be normal, and your perception of small amounts would be just fine. A more realistic issue is simply familiarity: if you're used to all your food being orange-scented, you'll stop noticing it, and probably won't notice slight variations, but you would still notice the absence.

If hypothetically someone really couldn't perceive normal amounts of basic tastes and aromas, then yes, they would have trouble knowing on their own how to cook food that others would enjoy. They could of course still follow recipes, or learn what works for others, and even be creative with guidance from others.