I typically associate "vivid" with intense visualizations, and I have a hard time visualizing things distinctly. I'm ok at imagining narratives and characterizations and "slice of life" analyses that become creative works, but I wouldn't describe them as "vivid" imaginings.

Personally, I don't think imagination or its vividness has much to do with the task of journaling. For me, journaling is more like a chronicle that (sometimes) becomes a source for creative work, rather than a creative outlet itself. I don't think you have to be very imaginative to be a good chronicler. I think trying to be "good at writing" in my journals is what made it so hard to do for a long time. Once I just let myself be mundane and boring, journaling got a lot easier.