I am quite sure, Chad, that you have hit the nail right on the head! Mr Waller was suggesting that any poet hoping for their work to read over and over (by being chiselled into marble, which lasts for ever) should look back to their roots.
When I first came across this couplet I thought that a short, snappy "gnomic" aorist would look good. I still do.
My next idea was to "rewrite" the words and sentiment but to replicate the poetic feeling as well. An English translation of my thoughts is...
It is necessary for any poet, who hopes to be read always, to read the old poets.*
By the time that is written out in Greek one has about 26 syllables (of course that number could vary, depending on one's actual translation, enormously!), which comes pretty damned close to being able to be made elegiac. Is it worth making the extra effort and going for gold?
*The two lines of thought in Waller's original being...
Poets that marble seek = any poet wishing to be remembered
Must carve in Latin and in Greek = even in C17 England the apparent everlasting *snob* value of the classics was accepted!!
Even while typing this I've considered...
To secure one's future, explore one's past
Interesting isn't it?
These are my maundering thoughts and I profess no expertise other than being a thoughtful reader, and writer who suffers from interminable cacoethes scribendi