Obligatory "anecdote isn't data" but as someone in a third world country who seriously considered studying in Germany, the language learning aspect was the least of my worries. I got to a B2 proficiency level in around a year and to C1/C2 within a year of that (for context: you need B1 to apply for citizenship and C1 to apply to higher education programs in German).
Getting the 9k, plus flight expenses, all the paperwork expenses was what proved to be impossible; in reality you need around 12k. It was all too much. I had no way of getting that amount of money.
In the end I decided to stay and get my degree here. Learning German was a great experience so it wasn't all a waste. Met some great people along the way and discovered my love for linguistics.
I also personally agree that this policy isn't necessarily helping Germany overall. I think the Blue Card program is a lot more valuable and should probably be more heavily "advertised".