Earlier quoted context omitted.
> Improving old code bases From my experience, I think there's a great need in large tech organizations for people that are able to advocate for and drive initiatives that can scale up efforts to improve old codebases.
I agree, but that won't happen until large tech organizations incentivize and reward maintenance work. See this related HN discussion about someone who left Google partly because they were not promoted for their documenting and bug-fixing efforts. https://news.ycombinator.com/item?id=16483241
But it's nearly impossible to find that kind of job because employers tend to go out of their way to hide the fact that they even have existing software, let alone that they want someone to work on it.