>>ut humans were put here for God’s loving glory and if the love capacity is there for many children, it is only right by God to follow suit.<<
That is an example of a good argument for fecundity. There are others, including propagating values, maintaining national identity and strength (witness Japan which may soon collapse), and others not so much rooted in “if it wasn’t for...”
Over-rigidity can kill what would otherwise be a good love-based exhortation.