Trying to preserve culture is good because it leaves choice in the hands of the individuals; they get to choose what parts to pick.
It's incredibly easy to talk about "survival of the fittest" cultures from a Western point of view, but ask almost any other peoples that have had their culture irreparably damaged by colonial policies, and you'll find a different mindset.
The individuals are doing that choosing when they choose not to preserve certain parts. They're going to abandon the parts in favor of alternatives that work better. The abandoned parts will no longer be passed down because they lack practical value - but they can be recorded.
Trying to preserve a static and separate cultural identity is pointless when knowledge, technology and our environments are changing quickly. At best the efforts are well-meaning and harmless. At worst, they present as a fetish where post-colonial guilt tries to turn the West into a zoo of distinct cultures.
This is only true in the naive case where every decision is made in isolation, completely free of coercion. In the real world, this is coming after many decades of attempts to wipe out cultures, being overwhelmed by entertainment and other forms of pressure – want to guess the odds of an indigenous person successfully getting their music published, stories turned into movies, etc. prior to very recently? In most colonial countries attempts to convert people assimilate meant that schools prevented use of native languages and traditions, often even separating children from parents, leaving multi-generation gaps where people are truly learning those things for the first time at middle age from surviving elders.
None of that is a neutral choice, and especially not one to make a historically irreversible decision. Choosing not to preserve something means it's gone forever even if people in the future disagree.
My overall view is somewhat Darwinian, with selection based on merit rather than coercion. Overt oppression of other cultures is obviously to be opposed.
It seems to me that the idea that, aggregate individual choices always give the best results, should be discredited by now.
It's totally possible for individuals to be trapped in game theoretical situations where they will lost very valuable things to them little by little. Ecology is the most famous example.
Anyway, the efforts for "trying to preserve a static and separate cultural identity" is something done by individuals that choose so, too. How could be otherwise?
It's incredibly easy to talk about "survival of the fittest" cultures from a Western point of view, but ask almost any other peoples that have had their culture irreparably damaged by colonial policies, and you'll find a different mindset.