I struggled with the same in academia. I found genuine beauty and value in improving something implemented. But I also felt a bit "stuck", as if I was just stuck in a groove unable to pedal up. I wasn't the only PhD that felt this way and spoke with others at the time about the feeling.

I think there's a point of diminishing returns where improving something isn't worth it. But I mean, if you're innovating at the level of a PhD, does anyone really know anything at all? You are, by definition, pushing the boundary of human knowledge.