Two things must be considered. The first is personal taste.
I have a neighbor who use to be a salesman/distributor for the Thanksgiving Coffee Company. He always bought the "Midnight Roast" from a local commercial roaster we both know personally. He brewed it in a drip machine. The only way I can describe these coffee beans is "very black and soaked on the surface with oil." it smelled worse than it looked. I roasted him a batch of my own blend of Colombian/Yemen Mocha and it was roasted in a Hearthware Gourmet (air roaster). He said it was the best coffee he ever had... but went right back to drinking the Midnight Roast. To each, his own.
You mention that you didn't like the caramel taste of the coffee from Starbucks? This is a taste that many strive for. The dark roast was ashy to you? And you prefer that? OK, but a (and dare I speak for the group in this way), a VAST majority of folks here who had beans that tasted ashy would dump them into the trash. Note that the header above states that this site is intended to be a "guide to exceptional espresso." Ashy is generally not a part of a flavor profile that this group looks for and considers a defect.
If you like the flavor of the coffee to come through the milk, use less milk. The second consideration is the relative tastes of various coffees
. It is not at all difficult to make an espresso-based coffee beverage that tastes better than a Starbucks cappuccino. If you were using their beans at home, the one thing you can be sure of is that the coffee was stale. My universal advice is: "Never buy coffee that has a "best if used by" statement on the package.
"Medium roast" doesn't mean much to me because it is merely a relative reference putting the beans between light and dark. Compared to the dark roasts that one sees in the bins at the supermarket, a "medium" roast would be darker than I use for espresso. The "light" roasts seen there are comparable to what I use for espresso at home. Sort of a medium to dark oak color with no oil showing, and maybe a few droplets on a small number of beans after a week's rest, but no oil when fresh.
As an introduction to coffee flavors, take a look at THIS IMAGE
of the SCAA coffee flavor wheel. It will give you an idea of the complexity of the flavors and aromas in coffee and how fine coffees are judged and discussed.