Why don't the Borg use genetic engineering and cloning?

[Griffworks]

... or that was never the intention from TNG and that same lack of intention lent itself to VOY deciding their own course. You also need to remember that however many years passed - both in the Real World and in the TNG/DS9/VOY universe - and that the Borgs agenda changed, as well. Especially when you throw Species 8472 in to the mix.