ASL is a language
American Sign Language and other signed languages are languages. It’s important to respect them as languages.
ASL is not English. It is a completely different language. Similarly, signed languages aren’t all the same. British Sign Language is completely different from ASL.
Signs are not universal, any more than spoken words are universal. The meaning of a sign isn’t always obvious just by watching; many signs are completely arbitrary.
Sign is not pantomime, and it’s not ad hoc gesture. It’s also not like symbolic gestures that are sometimes made up to accompany kids songs either. It’s a language, with all the complexities of language. The difference is important, and it needs to be respected.
In order to know what signs mean, you have to learn them. (Just like in order to know what spoken words mean, you have to learn them.)
ASL is not just gestures, any more than spoken languages are just sounds. ASL has grammar, vocabulary, and culture. It’s important to respect this and not erase it.