For Wallace, is the garden just a mere retreat from mundane life? What makes the reader sympathize with the character?

Wallace confides in the narrator, Redmond, that he is a haunted man. He says that he is haunted by a “beauty and happiness that fills his heart with insatiable longings that makes all the interests and spectacle of worldly life seem dull and tedious and vain.” However, this does not prevent him from achieving success in life, for he excels in school and in his professional life, and especially when he is able to concentrate on these things.
Wallace talks to the narrator about the door in the wall two times: once when the two are still students in school; and later when they are all grown up—actually just a month before his death. He says that he first saw the door when he was only five years old. Upon seeing the door, he had been overwhelmed by feelings of curiosity: “an attraction, a desire to get to the Door and open it and walk in.” However, these strong feelings were accompanied by great hesitation on his part to yield to the need to get through the door. In the end, he had submitted to the attraction he felt for the door, pushed it open and walked into the most amazing garden. He gives the following description of the garden to the narrator:

There was something in the very air of it that exhilarated, that gave one a sense of lightness and good happening and wellbeing; there was something in the sight of it that made all its color clean and perfect and subtly luminous.

Further, he adds that

in the very moment the door swung to behind me, I forgot the road with its fallen chestnut leaves, its cabs and tradesmen’s carts, I forgot the sort of gravitational pull back to the discipline and obedience of home. I forgot all hesitations and fear, forgot discretion, forgot all the intimate realities of this life.

He explains to the narrator that his return back to earth had been a harsh reality; he had been grief-stricken, disconsolate.
Wallace sees the door about four times as a young man but does not walk through the door to experience the garden. In his adult life, he sees the door more frequently, especially when overwhelmed by the struggles of life.
Thus for Wallace, the garden is more than “just a mere retreat from mundane life.” The garden represents the ultimate ideal life for Wallace. He dreams of it, yearns for the chance to revisit it. The garden encapsulates all those good things that Wallace desires but cannot have. The reader sympathizes with Wallace, for the garden almost ruins all the goodness that he could have experienced in everyday life. One wishes that the younger Wallace never had a chance to walk through that door the first time. Also, the fact that the door finally kills Wallace is saddening. Yet, the reader is not surprised by this event. The paradise that exists beyond the door is unworldly, thus unattainable except, maybe, in death.