Obviously I played the game WRONG. I had to dose myself up on mentats and magazines to be able to not kill the NCR general at the end.
It's *really hard* to not kill the NCR. Random factions like the Van Graffs and Crimson Caravan that are tangentially related to them and *very evil* give negative rep. Plus, they like to start shooting you for walking too close to a random door.
In the epilogue crawl at the end, I got a blurb about how I'd 'ignored' the 'vault 19 powder gangers' and let them institute a reign of terror and murder across the desert. Where the fuck was vault 19? It certainly wasn't anywhere on the main quest.
So, uh, yeah. At least I was actually able to finish it, which puts it head and shoulders above most Bethessda games where I lose the plot so hard that I never recover. Missing half the sidequests pales in comparison!