One of the qualities of being a good writer, for example, is being able to imagine things.
I would say this has little to do with being good (vivid) at it. I mean, like writing is not about much about being inspired by the muse and much more about putting in the work, day after day.
Imagination is ideas, and ideas are plenty. I don't know about you but I can have dozens ideas in a single days of which oftentimes none will survive the first attempt at using them. For me that's how ideas work: a lot of waste that will get recycled, sometimes very slooowly (I recently used an idea I first wrote down in... 2003, there is little in common between the 2003 note and the actual text I'm writing but at its chore it's the same idea).
What's much rarer is an idea turned into something usable/actionable... sharable. The difference between a (great/bad) book one can buy and the best book ever written that no one can buy because its was actually never written is that one author put in the work, the other thought about it ;)
I think Journaling can help a lot in making writing an actual habit (it cna also help putting some order in our own thoughts, but that's not the point). As for imagination, I don't think it helps much, at least it doesn't help me much as for me a journal is supposed to tell things that have happened in the day. Not things I imagine. Those would be put into stories.