A font format with an optical-size axis defined, as OpenType has, gives typographers the ability to trust type developers again, to undo the “san-serifization” of typography, and to reinvest in responsive typography with much better tools.
From logos, corporate identities, and simple or complex documents, to world scripts (whose ideal designs were not like Helvetica), optical size opens an avenue of trust from the type developer, looking with a critical eye for readability, clarity, and efficient use of space, at each type size.
Typographers should also understand that if there is an optical-size axis in a variable font, the way the new technology works, all the styles in the design space of the variable font are some optical size or another, making it possible for the developer to ensure a design space with weights, widths, and all other details best suited for use at each size of any other axes.
In that opening, there is, along with the fluid expression of size over an entire design space, the parametric values of typeface families across that size range. This can help replace experienced typographers of the past with guidance for knowledgeable typographers in the present.