Still no definitive answer on this one then?
I have asked a couple of other people about this, and the consensus view is that it means:
"even though it may be / even if it were [many times Plato's and Shakespeare's]"
(which I think is more or less what I said last time).
Some typical examples of this usage of the archaic "were it never so" (randomly Googled) in which the meaning is perhaps slightly clearer:
... but I cannot let this day pass without sending you some word or other, were it never so insignificant. (= "...even though it might be insignificant")
If the first of these fail, the Power of Adam, were it never so great, never so certain, will signifie nothing to the present Governments and Societies. (= "... even though it may be very great, very certain ...)
There are two competing theories about what "many times Plato's and Shakespeare's" means. The first is that "many times" just refers to the volume of material that the authors wrote (and hence the volume that is being rejected). The second is that it means "[even if it were] many times superior to Plato's and Shakespeare's [work]".