The Triptych Proposals [1] cover a lot of common use cases for submitting information to a server and updating part of a page. Something like that should have been possible to implement early in web history (I perceive some similarity to frames).
Modern CSS (and some newer HTML features) also reduces the need for scripting.
I very much doubt that "Enabling scripting was a necessary step for interactive websites." (emphasis added). It may well have been the most convenient and fastest way to get the functionality to the most users. With Javascript each website could provide functionality without waiting for such to be implemented by all browsers.
However distribution of power also leads to more complex trust relationships (even if one is confident that sandboxing is effective). Independent implementation also leads to more complexity overall.