I didn't lose my _passion_ though. I just redirected it. I've taken up woodworking, I've learned a ton about 3D printing and CAD, and my wife and I have our eye on getting a laser printer soon. I've travelled a bit more too, and have learned more about home ownership/improvement than I ever thought I would enjoy (turns out I do enjoy it!). I've started learning more about finance and economics, and took a random dive one weekend into geography so that I could try making a realistic D&D world map that took into account naturally forming rivers, coastlines, mountain ranges, etc.
On top of all that, I have a newborn daughter now and get to pour my passion for all of these things and more towards her as she grows, and getting to learn what it means to be a parent and how to do it better than my parents did (they did a fine job; but isn't it always good to improve?).
I think oftentimes this passionless burnout comes, like it did for me, from attaching too much personal worth to one single topic. May be different for others though.