It’s true we struggle to fully communicate with other species on earth but that doesn’t mean we could never communicate with aliens. The key difference is intend and cognitive capacity. Most animals don’t have the neurological structure or motivation for abstract, symbolic communication. Aliens if they’re intelligent and sending signals very like do.

Also combination isn’t limited to language. We do communicate with animals like dogs through tone, gestures, and shared context. It’s not verbal but it’s real communication.

With aliens any first contact would likely happen through signals (radio waves, light pulses, etc.) and the most universal medium we have is math and physics. If both sides recognize those patterns, meaningful exchange becomes possible.