I did not know how to explain that with lack of scientific understanding for a very long time. The only reasoning I can console myself with is each person is different, our sensitivity vary a great deal due to our diet, body chemistry and exposure to tea. But it is much more than that.
In Chinese term Yun is an intangible sensation. The Chinese translation is "containing compound", I suppose it means it contains substance of richness that can be sensed rather than measured. The term Yun often describes a musical piece of texture, density, thickness, range, width, layers with richness. The concept can be borrowed to describe tea as well.
Yun and flavor are two entirely different concepts in tea. More often than enough that high mountain old tree teas have thick rich Yun, subtle flavors that linger a very long time. While low altitude young crop teas have more obvious, detectable flavors. My advice to tea drinkers is emphasize less on the flavors, flavor is manipulative artificially by human hand, on the other hand the "contained compound" leaves are born nobly by older trees living in the environment that protect and nourish before they sprout. You can only feel them!
In scientific studies, three key substances influence the taste of a tea, here taste does not equate to flavor. Taste including flavor and texture, while flavor is only flavor.
1, Polyphenol = stringency
2, caffeine = bitterness
3, amino acids = sweetness and refreshing taste
Polyphenol ratio and amino acids ratio play teeter totter with each other, one goes up, the other goes down. Summer harvest, mature leaves contain more poly phenol, hence more astringent. Spring harvest, high altitude, younger leaves contain more amino acids, hence sweeter and less astringent, also less stimulating to the taste buds as astringency and bitterness. To less experience drinkers, there is less flavor due the the absence of those two flavors. High mountain and shade grown teas contain more amino acids than low altitude teas due to sun exposure. Polyphenol are substances released by plants to protect itself from the sun, insect bites and other environmental impacts, therefore the ratio goes up in Summer harvest.
Polyphenol by nature is a protective substance, therefore it also protects human as an anti-oxidant. Amino acids are in forms of proteins, amino acid residues form the second-largest component next to water of human muscles and other tissues. Hence it's a replenishment to nourish our body, and is the "essential" for humans. *quote from Wikipedia*
Teas that contain more polyphenol are processed in ways to emphasize on flavor, cover up or mute the enstringency and bitterness, enhance aroma by manipulating with roasting or oxidation in the case of oolong teas. While the best tea materials are usually less tempered with to preserve its natural greatness. Same concept as in food preperation, the best ingredients are less spiced in the the cooking process, Cantonese and French food are the finer examples of that. However a Szechwan person with a life long palate of hot spicy diet would not have the same appreciation for Cantonese cuisine, and vise versa.
My point being, you can't expect every tea drinkers have the same sensitivity to feel teas the same way. Otherwise, what are the tea growers going to do with the summer teas, and the alike. Or those who are lucky enough to discover the secrets of Yun would not have enough good teas to go around.
A flavorful tea stimulates your taste buds, a great tea stimulates you internally, energizes you.