Spanish according to the country
Duo should divide spanish according to different countries- like I want to learn the traditional (spain) spanish and not Latin American Spanish which they teach us.
That would take more of Duo's time and money. There are fewer than fifty million people in Spain, and they speak 3-4 different dialects. There are over 400 million Spanish speakers in the western hemisphere (as many in the USA as in Spain). I think Duo is dealing with reality. To begn with the Spanish you prefer, take a look at "La Vida Loca" online at BBC languages.
One problem with that is that you could do the same with the other languages offered as well. You could learn Quebec French as well as Parisian; British English as well as American; Iberian Portuguese as well as Brazilian. Why single out Spanish? The various dialects are just slightly different versions of the same language, anyway, mutually intelligible.
And Spanish, like some of the other languages, is the dominant language in a host of different countries and a second language in a bunch more. If you were to divide it up by dialects you'd probably have better than a dozen choices at least. Where should it end? Why bother? If you can understand one you can understand the others except for maybe some regional slang and differences in meanings or pronunciations of certain words, no big deal.
That's my opinion, anyway. If DuoLingo were to do that it would probably take them a long time and a lot of hard work for little reason.
I'd argue that it's very much dependent on the language we're talking about. For instance, in Spain, they use vosotros (2nd person plural familiar) - not something commonly used in much of Latin America, as I understand it. Lessons on those kinds of differences might be useful, which is all I was trying to point out.
The colloquialisms, on the other hand, are a bit of a different animal, no?