How do certain key objects, such as the burned house and the old quilts, focus the reader's attention on the basic conflict of the story?
The objects in "Everyday Use" are cultural heirlooms, symbols of suffering, slavery, and female domesticity. As such, they are worthless to outsiders, but valuable to the women inside the family as emblems of status and matriarchy. So, Wangero (explicitly) and Maggie (implicitly) compete over them, much like two daughters competing over their mother's love. Whoever possesses them by the end will be the next matriarch and family historian.
Usually, heirlooms are passed down to males by order of birthright: the eldest son gets the goods. But, in the maternal world of "Everyday Use," there isn't a worthy male in a country mile. So, Mrs. Johnson must decide, de facto style, who to bequeath the quilts, churn, and--ultimately--the house.
Originally, Mama expects it to be her older, more beautiful, more accomplished daughter Dee. After all, she has taken the name of two former matriarchs--Grandma Dee and Big Dee. She has been groomed for matriarchal status her whole life, but she turns her back on her culture by adopting another: the fad culture of a Black Muslim nationalist. She changes her name, appearance, and attitude. No longer is she a humble domestic; rather, she is a spoiled, arrogant, albeit educated, woman.
As such, Mrs. Johnson feels compelled to give the items, title, and legacy to Maggie, even though she feels unworthy. Mrs. Johnson knows these possessions are worthless, but--as a whole--they are meaningful to these women, for they are living documents of their domestic past.