They have lots of “stuff” but most of it is old stuff and probably not well-maintained. Many of the troops are sent to work in the fields. They don’t have the resources(i.e. gas) for much training.
IIRC their military needs several months to “spin up” to readiness. Any moves like that will raise the ire of the Chinese who see North Korea as a “little brother”.
Lets hope that NK don’t threaten China. They seem pretty bold and like to threaten everyone but then again maybe that is because they were allowed to be bold.