I think more generally worry about things you can change is a big net positive for the individual. Worrying about external things that you have no control over

I think more generally worry about things you can change is a big net positive for the individual. Worrying about external things that you have no control over is a huge drag on most people's lives. It leads to a lot of anxiety and stress. Sure there may be some individual that believes they cannot change something when they in fact can make a difference, but this is exceptionally rare. The more likely case is that someone can choose to focus on something small where they can make a difference, in which stoicism would guide them to make that difference as opposed to feeling dread about something that they have no control over. For instance, if you're concerned about climate change, one way you can go about it is to go to some big demonstration and yell about it (and leave a big mess in its wake). Or you can focus on the local, like cleaning up your own neighborhood which is something you can make a difference on. The local action will have more of an impact and be more personally rewarding.