See the first bullet point in the What kind of questions should I not ask here? section:
every answer is equally valid
There's no one "correct" answer to your question - you are asking for a list of equally valid answers, and as such your question is not constructive.
It's a perfectly valid question to ask, but there are some kinds of questions ...
First, let me say Robert did not really answer your question (and I don't mean the fact he only used the comment sections):
The comment to your first bullet point gives just a starter for an idea of one possible solution, but I would not call this an answer.
The comment to your second bullet point tells you very clearly why this part of the question is ...
IMO it's condescending form of question. Whose words would you use if not your own? Are you a plagiarizer? An android? Or maybe they want you to make up something ridiculous?
I can't remember the last time I was asked such a question, but if anyone did ask me one, I'd chafe at it.
That sounds like it could be a homework question!
Actually on reading it now it certainly reads like a homework/interview question.
I think you've identified the problem with this type of question in that it will end up with a "plethora of answers" each pretty much as valid as the next. In addition there doesn't seem to be a real problem to be solved here.
Thanks for taking this constructive. I would recommend to start with clarifying the problem statement. You wrote
I'd like to publish it somehow
which is IMHO very ambigous. Do you want to publish it as Open Source on Github? Just inside your team to another team member? Inside your own project as a library which can be reused by another project? ...
Using broad brush strokes, here's your question currently.
"I just started working on a large, legacy application."
"There appears to be a lot of technical debt within the codebase."
"I can't find any documentation within the code."
"Is this normal and should I get over it?"
I'm being a bit glib with my paraphrasing, but that pretty much nails it.
It was the first paragraph that caught my attention.
I thought this was okay, could have been a little more specific about what documentation was being asked for, but it sounded good:
I once was on a project where a non-tech manager had the team spending
half of every hour documenting what they just did so that someone with
zero understanding of the ...