I think you'll find that dark roasts are popular now because they have a more robust, classic coffee flavor that stands up to the fat of milk. Lighter roasts seem to come off as citrusy and less flavorful for two reasons. First, roasters tend to use V60s to profile their beans, and the V60 disproportionately removes citrus flavor. The second reason is that many people drink their coffee immediately after brewing, when in fact the flavor completely opens up after the coffee cools down to about 140 degrees (about the temperature of a hot water faucet in a home).
Try a darker roast if you put cream and sugar in your coffee. If you have a lighter roast, be sure to let it cool down to appreciate its benefits. If you buy a medium roast, keep in mind that each type of bean is unique, and certain beans have unique qualities that are highlighted by their roast, so don't assume that the flavors you enjoy are particular to the "medium" roast.
Finally, keep in mind that lighter-roast coffees actually have the most caffeine. This is because heating the coffee breaks down the caffeine molecule, so the longer the roast process and the darker the roast, the more caffeine is broken down.
In general, I shoot for medium roasts just because they're safer - I like the richer flavors from dark roasts, but most dark roasts are just burnt, which makes for a really bitter and unpleasant cup. You're absolutely right about the range of flavors, though - I tend to like nutty coffees (not nut-flavored), and citrus/floral/peaty tend to be less appealing to me. Light roasts seem to accent lighter flavors, like citrus, whereas the darker to roast, the more accented the round, full flavors like peat and nut tend to be.
I actually drink my coffee black (for health reasons; I realized that I was taking in a ton of daily calories in milk and sugar) which is what motivated me to find better coffee. When you're masking the flavor of the coffee with additives, it's easier to get by with bad coffee, but when it's just the brew itself, the tastes matter a lot more.
The lighter roast = more caffeine thing is actually (kind of) a myth; you get less caffeine per bean, but since the dark roasting process removes more water, you actually end up with a higher caffeine-by-volume content in darker roasts. If you're using the same volume of coffee per pot (say, 4 tbsp), then you may actually end up with more caffeine from a dark roast, since substantially more of that 4tbsp will be the coffee itself rather than water left unextracted from the bean. However, the caffeine differences between something like a robusta vs an arabica bean are very significant, so if you need more or less caffeine, you can pick a roast you like with a bean that gives you the caffeine you desire.
Most roasters worth discussing use a process called "cupping" to profile their coffees. Even those not worth discussinh are far more likely to use this controlled, direct immersion method, than a paper filter brewer like the Hario v60. Not sure where you're getting this from.
Try a darker roast if you put cream and sugar in your coffee. If you have a lighter roast, be sure to let it cool down to appreciate its benefits. If you buy a medium roast, keep in mind that each type of bean is unique, and certain beans have unique qualities that are highlighted by their roast, so don't assume that the flavors you enjoy are particular to the "medium" roast.
Finally, keep in mind that lighter-roast coffees actually have the most caffeine. This is because heating the coffee breaks down the caffeine molecule, so the longer the roast process and the darker the roast, the more caffeine is broken down.