The Importance of this is being way overstated and not understood by certain people here.
I'm by no means an expert in East Asian geopolitics, but this has the potential to totally realign the region, yes?
No, not at all. Its more of a joint statement to develope defense ties, for example defense sales, if anything. It is nothing close to a mutual defense agreement, like what ROK has with the US. This is fairly normal in the world of Geopolitics, between countries, even ones that are not regularly aligned. Its meaning is relatively little.
However, it is indicative of a direction. A direction that has already been visible with the far more important ROK-Japan trade spat and the abrogation of their intelligence sharing pact. There is a frustration in South Korea with the US and it being percieved as being a bit Pushy and biased towards Japan. But South Korea is going to continue to aligned with the US for all forseeable future, Moon and all major Politicans in the ROK have been perfectly clear about that, and the recent Russian/Chinese intrusions into South Koreas ADIZ and the North rejecting denuclearization will mean that the US-Korea alliance will remain.
Very informative, thank-you!