For an extension like noscript or ublock, yes, it's hard to draw a line. One site uses one feature set, another site uses a different feature set, and if you draw the line around the union of those feature sets then it's too broad. Ads complicate things even more, because a simpler technology makes it easy to filter them.
I don't think the solution is in trying to draw such a line. I think the solution is to build something that covers 80% of the use cases, AND makes it sublimely easier than the technology we use today, AND is backed by someone with the power to deliver it to users.
There are examples in our history where we rejected a complex technology in favor of a simpler one, so there is some precedence. Remember HTML 3.0?
I don't think the solution is in trying to draw such a line. I think the solution is to build something that covers 80% of the use cases, AND makes it sublimely easier than the technology we use today, AND is backed by someone with the power to deliver it to users.
There are examples in our history where we rejected a complex technology in favor of a simpler one, so there is some precedence. Remember HTML 3.0?