I spend time HN because I am no where near the smartest person and I tend to optimize for learning. But that is my nature...and it only works for me for some odd definitions of "works".
I don't really have an accurate context for Japan's employment landscape - other than believing it is somewhat different from the US. So I don't feel comfortable being specific. My confidence in my imagination fails me unfortunately.
The startup world may be influenced a lot by Mark Zuckerberg's motto of "Move fast; break things."
However, I don't think it's a good goal to aim for.
Like @andreasklinger and @hashkb said, you should have agreement with your engineers about your limit.
Refactoring can never be enough, because we always try to improve, try to be better.
You can think about the "later days" when you can come back on your codes and fix those crap codes, but you know you won't. The bigger the debt for now, the costlier it will be in the future.