- DHS did not have the talent base to pull of a lot of its cyber mission, and probably never will
- Budgetary scale in DHS to address cyber issues is minimal and probably always will be
- DHS has forever lost the trust of the constituencies it needs
That last bullet point is hammered in by Kirstjen Nielsen's career implosion as she promoted harsh anti-migration methods but is emphasized by the current DHS twitter account, which is now a partisan parody of what you would want to see from an organization trying to get cooperation from large technology companies.
Many people, myself included, always wonder at the efforts of government agencies to turn themselves into budget anti-virus companies. But strategically, the one thing DHS or DOJ has to offer is their reputation. When they make an attribution or statement from their official Twitter feed, that has to be believed by everyone. And we don't have that anymore, which is going to have implications up and down the cyber domain.
In some ways, having an independent cyber agency is the only solution. Untainted by the other missions of DHS, without the history of DHS, without the offensive mission of the NSA or military, and perhaps set up in a way that allows private industry to trust it with a respected technical leadership. I don't see this happening any time soon, however, but it might be something for a future administration to consider.