Btw this happens in most companies, tons of tech debt. And those who created that st are off onto new projects recreating the exact same mess all over again.
It is a cycle that never ends.
Only chance is to join early and be in for the long run.
It's s lot of fun with the right attitude.
And hopefully no one else regrets it...
Thus is the circle of (engineering) life.
Just kidding. Please write maintainable code.
Not in the requirements, sorry.
Most people don't know how to do this, because it's actually hard, and I don't think it's being taught much in programmer education.
I certainly had to learn "on the job", and probably spent 10 years before I got good at it.
I learned the most by fixing bugs. After a while, I started seeing the patterns of why this bug had occurred, and started writing code do avoid the traps.
I prefer the term troubleshooter specialising in legacy code, but "code janitor" definitely has felt more appropriate at times.