Job prior to this one was at a raw stage startup (two cofounders, both new college grad). Most of the back-end code base was written by a now-departed first emp

Job prior to this one was at a raw stage startup (two cofounders, both new college grad). Most of the back-end code base was written by a now-departed first employee (also a new grad), and it was a trash fire. The "tech" founder had a decent front-end code base, where they were very much doing what you describe: I could tell which parts of the code were written when, based on their skill growth, etc etc. As an employee, it wasn't my call when to pay down the back-end's debt. I was very happy to get out of that. Anyway. Yes, it's different when it's your debt, and what makes it your debt is then whether you're the one who decides when to pay it.