If you're 15, then you have already received free government funded latvian language courses for 9 years in school. It's part of the curriculum. You'd have to be especially lazy to not be able to pass the citizenship exams.
What if the parents chose to send the kid to Russian-language school?
In any case, you have a point that if someone WANTED to integrate into Latvian society, they could. What I'm questioning is the desire.
Having immigrated to US and adapted to that society, I'd have to say that moving "back" to the country where you already speak the language and identify with the society is quite a bit easier than to fully integrate into something you are not used to. It's all in the will of a person and the economic incentives to do so. For me in the US, I had the resolve and very strong financial against to be had if I followed through.
If you take Switzerland as an example, their extremely high citizenship requirements are well supported by the high standard of living and long term benefits. Unfortunately, Latvia, together with the rest of the Baltic states does not yet have such a strong position. I suspect when it does, such complaints will end, as people will be happy to do the work for the reward.
