Since Darcy is the heir of his father's Pemberley estate and to his father's fortune and farming income, then he can marry just about anyone he pleases without incurring too much scorn from society because no one would dare to ostracize someone of such high social and monetary standing as Darcy. However, in marrying Elizabeth, there is little that society could offer against his choice except for the obvious criticisms against her negligent father and spoiled, ill-behaved family.
While it is true that Elizabeth has no significant income of her own to contribute to a marriage, she is the daughter of a gentleman. As a consequence she is fair marriage material for any member of high society (lower than royalty) who has the wealth to accept a virtually penniless wife. Plus Elizabeth's personal charms and elegance and good mind make her suitable to a higher society than she has yet associated with. Therefore, when Elizabeth's relations are not around (excepting Jane and the Gardiners) society will have little or no reason to dispute Darcy's choice in marrying Elizabeth.