SDLC can be made to be inefficient to maximize billable hours, but that doesn't mean the software is inherently badly architected. It could just have a lot of unnecessary boilerplate that you could optimize out, but it's soooooo hard to get tech debt prioritized on the road map.

Killing you own velocity can be done intelligently, it's just that most teams aren't killing their own velocity because they're competent, they're doing it because they're incompetent.

And note this is one instance of task, imagine a team of people all using your code to do the task, and you get a quicker ROI or you can multiply dev time by people

In practice, is only quicker ROI if your maintenance plan is nonexistent.