We often refer to artists or writers as being creative, but the actual definition of creativity is:
"the ability to transcend traditional ideas, rules, patterns, relationships, or the like, and to create meaningful new ideas, forms, methods, interpretations" - https://www.dictionary.com/browse/creativity
So whilst artists and writers often gain their fame from writing something imaginative and unique, developers also exhibit this skill albeit in a slightly different way.
Traditionally it was thought that the left side of the brain was for logical thinking, and that the right side was for creativity. This way of slicing the brain has been debunked - we all use our brain in equal measure, and it's down to other aspects of our personality that dictate how creative or logical we are. Therefore, developers can have a lot of creativity! Yet in their day-to-day lives they probably don't get to pursue creative outlets in traditional ways.
If we consider only the nitty-gritty backend developers, even in this seemingly uncreative environment creativity can shine. Whilst the code itself may be completely logical, to be able to split the client's requirements into sections for development requires a certain level of imagination.
Problem solving itself is a form of creativity as you're forced to discover new ideas to overcome obstacles. As developers, we can increase our inventiveness not only through artistic outlets, but also through problem solving. One simple task you could do is that every time you come across a problem, consider three different solutions - and don't limit yourself to only what you know either! Assume you'll be passing the work to someone else to develop and consider options which might, at the moment, terrify you as a developer.
This not only improves your problem-solving skills, but also provides you with a bank of solutions which you can pull from when you need to; and hopefully in a few months you'll look back on your possible solutions and no longer be scared of them.
Ultimately having a creative outlet is so much more than creating an incredible piece of art, or writing a symphony; it allows us to see the world in a different way. It sparks our imagination and opens our eyes to different ways of thinking.
"Creativity is the source to improvise solutions to problems for dominating complex systems such as software development" - Daniel Graziotin
"Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution." - Albert Einstein