you are correct that you might like the taste of dark roasted coffee as a personal preference, but that's not a "quality" quality, it's a taste preference. But you can make that strong dark coffee out of virtually any beans, just roast them to near death, it doesn't matter what you start with. Like chocolatey notes? you're in luck! that's called Brazilian coffee, and it's really really cheap to buy the beans.
You may not like more lightly roasted tea-like coffee flavors, but they have more distinct differences, fruit notes, etc, that you would easily be able to taste and differentiate between, even if it's not your preference.
being a barrista gives you a leg up on knowing about the coffee you tried regularly, but not on the coffee you haven't, and it takes a substantial amount of time to develop a palate, as with wine tasting.
we used to have two different guest blends every week at one of the coffee shops I used to work at. So I've tasted a lot of different varieties of coffee. I prefer dark roasted coffee.
And no, you can't make what I'm talking about out of 'virtually any beans'. You can make burnt, shit coffee out of any beans. They are different things.
Just because you have a preference for light fruity coffee does not mean you get to determine what is 'quality' for the rest of us.
dark roasting coffee decreases the subtle differences between beans. The more you roast, the more the aromatics disappear. full stop, theres no way around it. You are not going to buy the most expensive coffees to dark roast unless you are a fool. But as you say, there are differences between heavily roasted beans, as an example I mentioned, some might have chocalate notes.