They have they languages, we just watch them talk in English, because it would be stupid to create another language, make actors use it and just add English subtitles. For example Eternals in 3000 B.C. couldn't speak English, because it didn't exist back then.
However we also have to explain interactions between aliens and humans who don't know alien languages, for example Iron Man and Thanos. From what I remember in GOTG Vol 1, when Star Lord got caught and is standing behing glass in prison (the middle finger scene) it is shown that he has a translator chip (on the screen next to him). So maybe these things are popular and every alien has them? That would be the best explnation in case of Guardians, Thanos and his children.
In case of Asgardians, they probably learn human languages, because Earth (Midgard) is one of the 9 realms. Also they live for thousands of years so they got a lot of time for studying.
So the best explan4tion I have is- Asgardians learn English and possibly other humans languages. Other aliens that are shown to speak to humans not knowing alien languages (Kree, Skrulls, Thanos, Children of Thanos) have the translator chips. I agree that it is kinda weird, because Earth isn't the center of the Universe and it's inhabitants recently haven't even known about aliens.