In the context of the example I'll grant that it's a bit silly to think of it as an E7. In the context of a band scenario, it might make perfect sense. If you'r

In the context of the example I'll grant that it's a bit silly to think of it as an E7. In the context of a band scenario, it might make perfect sense. If you're playing a jazz tune from a lead sheet, it might be very reasonable to mark that chord as an E7, and the bass might be playing the root, in which case thinking about it as a viio7 would miss some context. The problem with music theory is that it's _extremely_ contextual, and I think you have to at least get a sense for some of the "rules" of chord construction to be able to make sense of the notation. Music theory is just a language for talking about sounds and harmonies, and while there are cases where "just focus on the intervals" would make sense, there are just as many times that it's useful to say "it's a ii-V-I in Ab major." Having the language be based on the diatonic chords of the key you're in can make it easier to express a lot of different concepts in a shorthand, instead of having to spell out the intervals of every chord you come across. My advice to folks learning music theory would be to check out the Signals Music Studio channel - that dude has helped me make sense of theory concepts that I never grokked in years of playing music. I think it's really one of those cases where you have to get a good sense for the language before you start to get frustrated by the limitations and blemishes of the whole system.