I think it is a question of what is the most moral decision: if we are unable to reconcile the question of objective or subjective morality, we may be able to sidestep the issue. Can it objectively and subjectively moral to interfere? No, because our judgements would have to be objectively superior to impose them on others, otherwise another's objectively superior values would be preferable.

Can it be objectively and subjectively moral to not impose our morals on others? Yes: we can make all sorts of arguments for this.

Objectively: Our judgements may be superior, but we may have a higher priority than imposing those judgements on others, including -

1. (assuming values and morals develop and evolve linearly, big assumption I know) allowing others to develop those values themselves
2. if imposing our judgements does not benefit us in some way, then conserving our resources to efforts which benefit us and not others
3. not entangling ourselves in situations which have unpredictable and potentially complicated outcomes
4. any of the reasons why a moral realist would still argue against the invasion/colonization/deployment of "advisors" to a foreign environment.

Subjectively: for the reasons I mentioned before.

But I think even this isn't the right way to an answer: I'm arguing against an anthropocentric worldview, more akin to a deep ecology perspectives, which says this: the non-human should be respected and regarded as having certain inalienable legal rights to live and flourish, independent of its utilitarian instrumental benefits for human use, divorced from human conceptions of value and morality, recognizing an intelligence and sociality completely alien and having evolved and developed entirely removed from anthropocentric perspectives and reasonings.

There is a question of if alien culture, intelligence, and sociality can be translated into something comprehensible to humans. For the most part, we are lucky thanks to ST's ancient astronauts, but truthfully, if aliens were not distant cousins, we would have no place to judge them.