My brain's kinda mushy right now, but if I'm understanding your post correctly, I can really relate and was just thinking about this. For years I kinda blamed it on depression and assumed it was just part of that and would go away, but I'm becoming more and more aware of it being there even aside from depression, too. It just feels like there is this drive or something that other people must have in them that I am just totally missing. I'll want to do things sometimes or at times feel passionate about things and plan to get more involved "in the future" or "when I'm feeling better," and when the time comes I just don't, or the time just never comes. It's like I only want to do them in theory, and I don't know why.

Sorry I don't really have much advice, but you're not alone. Maybe try thinking of things you think you would do if you were being less passive in life, even starting small, and force yourself to do them. I'm just not sure how to change the actual feeling or whatever the root of the problem is.