A lot of other languages allow + to concatenate lists/arrays/sequences, even merge dicts/objects/maps. Languages that don’t have those semantics often have much safer and more idiomatic ways to join data structures (see lisps of all sorts) in ways you wouldn’t immediately expect if you’re coming from this perspective.

Adding two arrays together isn’t the problem, it’s a perfectly obvious thing to do. Adding two arrays together and getting a new language out of it is bonkers.

Edit to add: I work in JS/TS almost exclusively. This isn’t a chip on my shoulder criticizing a language I’m not invested in.