I work on performance and I enjoy it even more than writing features, honestly. There’s much more freedom in it in a professional setting because you generally get to define the subtasks under the goal of “make it faster/more efficient” whereas with a feature you’re usually told what specific thing you’re supposed to make, and your flexibility is usually just picking how to implement that. And the problems are almost always challenging and require technical (and occasionally, political) insight to fix. With features you might ship something that’s loved or a dud, but improving the performance of something is basically always a good thing.