I wish to understand the boldfaced part of the sentence The true poet is not an eccentric creature, not a mere artist living only for art, not a dreamer or a dilettante, sipping the nectar of existence, while he keeps aloof from its deeper interests., which belongs to J. C. Shairp.
The key to the meaning is dilettante, which ODO describes as
A person who cultivates an area of interest, such as the arts, without real commitment or knowledge.
Sharp uses the image of a bee flitting from flower to flower as a metaphor for a dilettante’s lightweight and possibly fickle interest in the arts (“the nectar of existence”).
There is no attempt to immerse himself in the arts, to pursue a deeper interest. The dilettante disdains that. Using the word aloof, “conspicuously uninvolved” [ODO], Sharp indicates that the dilettante actually feels that such an involvement is beneath his dignity.
A true poet, on the other hand, jumps in with both feet.