I'm of the opinion that almost all culture has value and thus value is lost if the culture is lost. For example, Mexican food is a cultural item - it would suck to lose it!

I also think it's not racist to say that some cultures are better or worse. After all, you essentially can choose your culture. I make no claims about whether immigration would improve Latvian culture, it may well, but that isn't a guarantee. For example, imagine them absorbing a culture with morally offensive values - racism, sexism, phobia of religions, etc. Such things are possible and it would be tragic to see a country's culture adopt those values due to immigration or cultural absorption.

Now to be clear here, I'm not implying that's going to happen, I'm just saying that sometimes culture may be worth preserving as its own merit.