What does the suffix -ist mean in the word pianist?

"one that performs a specific action"

d) the narrator even suggested that the white whale, moby d, was ubiquitous and present in every ocean at every moment.  

he is. some of his decisions were very irresponsible and did lead to the death of both romeo and juliet, such as him marrying them too quick or him not clarifying romeo's plan with him.

basically he did not think things through well enough or at all.

hope this