I respect your perspective, but it's one I mostly see in younger people. It's basically that personal achievement and being able to single-handedly deliver things are the most meaningful outcomes of work. The perspective that I've come to accept is that very few things that actually impact the world can come about this way. We didn't put men on the moon because some genius did all the calculations and fabrication himself (even von Braun was only one part of a very large organization), we did it because thousands of smart and determined people set aside their personal ambitions to work together on something great. The downside of this, of course, is that everyone is effectively a cog in the machine and it's easy to get demoralized that your contributions don't mean much.

I guess what I'm trying to say is that if you want to actually change the world, you're unlikely to do actually do it at a tech startup. You're instead likely to talk a lot about it while the real world-changing things are happening elsewhere. But you'll probably be happier at the startup because you get more of that magic combination of autonomy, teamwork, and quickly tangible results. I just personally get frustrated that almost every startup and its employees act like they're working on the biggest problems in the world when they just... aren't.

Edit: forgot to mention. I know two people who left ULA for similar reasons to you and went to SpaceX. They loved working at SpaceX in comparison to ULA because the level of company ambition, speed, and impact was so ridiculously higher. However, one of them left SpaceX to go to a smaller aerospace startup and the other is now at Raytheon for the superior work-life balance. I'm not sure what the lesson is there...