Peaceful contact with aliens would tell us something fundamental about the nature of ethics and the universe.

Advanced aliens do not need any material resources or real estate from humanity. We can already interpolate that from existing science. So that is not the reason why there are here. And we know they haven't exterminated us already centuries ago.

Instead it would tell that we share some fundamental values like curiosity and diversity with alien species - as long as they evolved through natural selection and had to raise and teach and love their children. As long as they had to find productive ways to work together as a people.

We would realize that we are not alone and that we are being judged. That we can't just endlessly bulldoze the galaxy and that there are limits to acceptable behavior. Because there is always someone more powerful that could smash us, but they already didn't. That certain ethical ideals are fundamental properties emerging from the universe itself.

It would be a powerful counter to the current nihilistic materialism, that we need to start working to improve our culture.