As I am not your downvoter, I can comment freely. This is terse advice with little explanation and no alternative provided. But I wonder: which of “cliché, catch-phrase, metaphor, or slang word” do you consider this use of the phrasal verb
boil down? The OED doesn’t say it is any of those things. Rather, it gives the primary sense of
boil down as “to lessen the bulk of (anything) by boiling”, along with a figurative sense of “to condense, epitomize”. I presume you object to the common figurative sense used here as inappropriate to the register of a formal research paper. Please expand. —
tchrist 1 min ago