Objects made using an Art Nouveau style are crafted in such a way that they are as much a functional object as a piece of art. If art is a finality without an end, as it is the result of a process that has no other purpose than to exist on itself; And function is defined by a set list of criteria that define the object, it is only natural to ask our selves if this fusion of art and function is relevant.
Pugin, who was an important figure of the Gothic Revival, would have been extremely critical of this style as it displays its opposition to “the true principles of art and design” and displays “cheap and false magnificence” (A. W. N. Pugin, 1843) because of it's ostentatious nature and the fact that it displays decorations that wouldn't be, according to Pugin, appropriate decoration for the function that the object serves. A member of the Arts and Craft movement would hold a similar argumentation. Hence from their point of view, the Art Nouveau style is irrelevant as it's fusion of art and function is fundamentally contradictory in nature.
For Kant, the question of beauty in art is distinct from that of the function. Jugging if an object is functional is the same as proving a scientific theory. It is applying a set of universal criteria to a singular object. On the other hand, the “reflective judgment”, jugging of the beauty of the object, can not claim to be universal nor can it be associated with concepts of utility or pleasure. Thus art is totally distinct from the function of an object and are not mutually exclusive.
To conclude, because art and function are not mutually exclusive, one can not say that the Art nouveau style is irrelevant. On the other hand, this does not mean that one must decorate an object in such a way that it becomes a piece of artwork, it can be done or may not be done as the designer sees fit.
Pugin, A.W.N. (1843). An Apology for the Revival of Christian Architecture in England. London, Great Britain: John Weale.
Kant, E. (1781). Critic of pure reason. Riga: J. F. Hartknoch
Kant, E. (1781). Critic of practical reason. Riga: J. F. Hartknoch