Rye, The Spice Of Life.
"It's an acquired taste" is always a ephemism, not an expression with a precise meaning in it's own right. If somebody uses it, you need to find out what that specific person means by it, because what they mean may be different from what somebody else means when they say it.
If that person is talking about specific products within a category, specific brands or even specific expressions of brands, that person may be refering to what is, also euphemistically, known as a challenging whiskey. Often in bourbon-speak, these are very old products. In scotch people will say that about heavily peated whiskeys. It generally means (a) unfamiliar, and (b) intense.
But "it's an acquired taste" almost always means, "you might like it if you get used to it." But, in truth, the "might" means you also might not.
But sometimes when people say "it's an acquired taste," what they're thinking is, "you're a wuss."
Col. Charles K. "Crotchety" Cowdery
"Whiskey Don't Keep."