C-O, C-N, and ionic bond strength

I'm working through EK Chem book and it says since nitrogen will share electrons more with carbon it will make a stronger, less polar, less reactive bond than a C-O bond. I would have thought that the more polar, the shorter and stronger the bond.

If C-N is stronger than C-O because it shares it's electrons more, why are ionic bonds so strong when they are very polar?

Thanks!