I think the issue here isn't the hub itself, but DL's lack of issuing a waiver when they knew well ahead of time it was going to be an ugly day that could quickly domino.
The Storm Prediction Center at NOAA forecasted a "high" probability of Severe Storms in Atlanta on Wednesday, and that is essentially the highest level/warning they can issue (and rarely, rarely ever do), and yet DL didn't issue any sort of waiver, even during the middle of the day when the chaos had already begun.
In this sense maybe ATL is too big, because it is virtually impossible to effectively issue a waiver ahead of time or reroute customers via other hubs simply because so much of seat capacity is routed through it. Nonetheless, I'm still pretty opinionated about the lack of the waiver, it's ridiculous and has been a nonstop headache for me these past 2 days.
I showed up to BWI this morning to find my flight cancelled after having it cancelled last night as well, and that I'd been rebooked out of IAD this evening (which is now...also cancelled). Finally broke down and bought a full fare ticket on United instead.