It's a complicated issue. Part of the problem is nobody really wants to fix it because the costs will be enormous. When and if the regime falls it's going to take tens of billions of dollars in aid to keep it from destabilizing South Korea. Not to mention the massive refugee crisis that will occur. I'm pretty sure that's one of the many reasons why China hasn't dealt with it. Because the vast majority of refugees would go north across their border.

China has made it clear they aren't particularly thrilled with the idea of having someone not under their thumb next to their border as well. As a consequence of that... the "best" scenario would probably be China invading. But "best" is definitely in scare quotes as that could go VERY wrong very very quickly. I think the PRC is aware of that too. So unfortunately that means the DPRK will starve, because the realpolitik is such that solving the issue is just not a tenable solution for all the other parties.