I work as a developer now. Over the past couple years, I helped launch a few different really cool products, which you may have used or heard about. These two years have been a constant high with insanely busy work weeks but I loved every minute of it.
I'm currently in a phase where I still get satisfaction from design and coding but the things I have to work on right now just aren't that interesting.
I'm not feeling a high from my current work. It seems trivial, boring, reducing tech debt that I just don't find interesting at this point in my career.
The dopamine release isn't there and my previous work was giving that to me daily in large quantities.
I'm considering changing teams.
At some level though, I am in the same boat as you. I don't want to just write lines of code. I want a bit more.
Since this started happening, I've enrolled in courses on Coursera and Khan Academy. I'm leaning about deep neural networks and machine learning. The amount of information is staggering.
I have one stream on just relearning or newly learning some of the math. I have another stream just watching ML and neural net tutorials and articles to become as familiar as I can. Then, there's a third stream of actually coding through some exercises.
Motivation comes and goes. Stay disciplined and find something that really excites you.
If you're just done with development, maybe consider a step into management.