The nature of texts like Wuthering Heights is that "modern" critical perspectives can help us make new and valuable interpretations. When you ask whether such approaches can "confuse" readers, you seem to assume that there is a "right" way to read the text, but such "right" readings not only do not exist, but seeking them out can obscure or even destroy the "literariness" that careful reading seeks to reveal.
In the case of Wuthering Heights, post colonialism has been used to understand Heathcliff's origins and outsider status; semiotics has been used to understand the differences between the Grange and Wuthering Heights; Marxist readings have explored the class differences between Heathcliff and Catherine; feminist readings have examined the text in terms of personal agency and the nature of male authority. A phenomenological interpretation would try to reconstruct the totality of meanings ascribed to the novel, or a kind of "history of meaning."
Each of these interpretations helps us to a richer understanding of the novel as a work of art and sheds light on the novel's enduring and changing significance to modern readers. While it may seem "confusing" to be presented with such a multiplicity of meanings, the "truth" about Wuthering Heights or any literary text is that there is room for all interpretations at the same time.