Except for the fact that it is designed to keep you coming back and hopefully paying them for the privaledge whilst making people believe they are learning something useful.

It is in fact counter productive to actually learning a language properly. I used it for a year and a half trying to learn Spanish and in that time I never really learnt anything of worth. On top of that my native Spanish speaking girlfriend told me on numerous occasions that the things it was "teaching" me were flat out incorrect.

I learnt more useful language skills in a month on Busuu than I did in a year and a half using Duolingo. So yes there is a lot of hate because it wasted a lot of my time for absolutely zero benefit and in some cases taught me the wrong things so I had to go back and "unlearn" all the bullshit it constantly pushed to me.

It isn't a tool to bridge a gap, it is a word game designed to get you addicted to "streaks" and then hopefully remove money from your wallet under the guise of teaching you something.

People that seriously want to learn a language should be dissuaded from using this trash app as it is only counter productive to the learning process, they should instead check out Busuu or listen to Language Transfer which is free and vastly superior!