You are partially right about the variability in preferences for sugar, e.g. there are people who like very much sweet wines, but who do not like at all dry wines and there are others who have the opposite preference, e.g. my mother liked only sweet wines, while my father liked only dry wines.
Nevertheless, the effect of sugar is more complex. For example, I do not like cocoa alone or in too high concentration, as too bitter. Sugar is pleasant, but when alone I do not care about it, I prefer most food with no sugar at all.
On the other hand, I find addictive the combinations of sugar with certain flavors, e.g. sugar + cocoa or sugar + vanilla. So, at least for me, the combination of sugar and cocoa has a very different effect than each component alone.
Nevertheless, the effect of sugar is more complex. For example, I do not like cocoa alone or in too high concentration, as too bitter. Sugar is pleasant, but when alone I do not care about it, I prefer most food with no sugar at all.
On the other hand, I find addictive the combinations of sugar with certain flavors, e.g. sugar + cocoa or sugar + vanilla. So, at least for me, the combination of sugar and cocoa has a very different effect than each component alone.