How does that even work though. "Hit the ground running"? It takes me months to get into a codebase and such a small thing as get it to build might be a multiple week hurdle if the guy you replace is gone.
I may not be able to refactor the system to use micro services or whatnot, but to dig into the code and start fixing some bugs or even add a small feature has always been a week 1 goal for me (and one I set to the people I manage now).