Intermingling business and presentation logic is fine - even preferred - when they are tightly coupled. Lots of “business logic” is actually just presentation logic anyway.
I don’t think the JS community is going to make the same mistakes Rails did. I for one am glad the days of highly mutative, untyped MVC are coming to an end.
Presentation logic isn't business logic, and mixing both will create severe headaches later on.
The point is more, most apps just don't have any business logic at all! It's very often just some CRUD on some data entities, and the rendering of those entities. CRUD isn't business logic.
I don’t think the JS community is going to make the same mistakes Rails did. I for one am glad the days of highly mutative, untyped MVC are coming to an end.