The reason why some things are thought “new,” which are not really so, is the imperfect record that exists of preceding ages among their successors.
those that ... come after - that is, those that live still later than the “things, rather the persons or generations, Ecc 1:4, with which this verse is connected, the six intermediate verses being merely illustrations of Ecc 1:4 [Weiss], that are to come” (Ecc 2:16; Ecc 9:5).