I think a good engineer can do both roles. With enough experience, they know when it's time to refactor and build nice fresh code. Other times they will know

I think a good engineer can do both roles. With enough experience, they know when it's time to refactor and build nice fresh code. Other times they will know when to just keep things running until there is time to rebuild properly. Though, if I have to pick one, I would say #2. It's harder to understand someone else's code and to keep it running smoothly. Though a good engineer may not be happy to stick around in a company that refuses to invest in their code properly. But good companies can have old code that should not be heavily invested in. Likewise, I think young engineers that have never worked with old code under appreciate how it ages. In comparison, my parents' have owned some very old houses. They have had handymen that install things like counters and cabinets. Every piece of wood needs to be measured in 3 dimensions. Decisions need to be made about which surface to make something parallel to. They operate in 3d and plan for eventual settling. Folks that only work on new houses may not think long term since they rarely need to live with their (or others') decisions.