Whether it's as sophisticated as other launch systems or not, the fact that North Korea can successfully launch a satellite means it's on its way to putting ballistic missiles into space as well. This is a next-level threat to Japan, South Korea, and the US, to which each respective military should be concerned. South Korea can point out flaws in the North's technological pursuits all it wants, but the West cannot be complacent as Pyongyang works with the likes of Russia and China to advance its lethal rocket programs.
Kim Jo Yong hasn't rejected the possibility of dialogue with the US, only the current, disingenuous ones being offered as Washington continues to ramp up its military presence in the South. Pyongyang has every right to develop the same defensive security measures that its increasingly aggressive adversaries have built. As for quelling tensions, that's up to South Korea and its antagonistic partners who have yet to stop provoking the North militarily.