The main translation used to be "advantage" I think, but it turned out to be a rather bad translation. "zaleta" is a good quality of a person, a 'plus' of a given solution, something in that direction. Basically "wady i zalety" is something like "minuses and pluses" of something/someone.
I don't think 'advantage' is old fashioned. I'd like to understand the distinction in Polish between 'zaleta' as 'talent' which would be a natural trait, and 'advantage' which could easily be a feature of the person acquired through their history, education, class etc. Does 'zaleta' cover both of these meanings?
Well, I translated it is 'I do not have a lot of advantages'...which is perfectly good English (not old fasioned at all) and the words translate as such. I would never say the 'correct' answer in English. If I was going to use 'qualities' then I would say 'many' rather than dragging myself over the stony stream bed of 'a lot of'.