Any help for sagging pale green leaves on non-flowering magnolia tree?
It sounds like your tree may have a nutrient deficiency. Pale green leaves can be a sign of lack of nitrogen or of lack of micronutrients, and lack of flowers can indicate a phosphorus deficiency. I recommend applying a balanced NPK fertilizer ase described in this article:
Organic options like compost or bone meal (provides phosphorus) are also available. Magnolias also prefer slightly acidic soil (pH 5.5-6.5), and this will help them absorb nutrients better.
Alternatively, if the magnolia is growing in dense shade, lack of light may cause these symptoms. Partial shade is fine.