> They hated each other and progress was very slow because they could not work together at all.

Been there. And often gets worse when the "ends-justify-means" camp (1) collects velocity points (that's the most important thing, they decided to gain the system that way) and people who care about velocity (typically management) are happy but... (2) leave a path of destruction in their wake that slows everyone else down, decreasing the productivity of everyone

With refactoring, consider 2 things (1) How bad / ripe for simplification is the code (2) How much is it changing

If its bad stuff but nobody needs to deal with it, I say leave it unless it has dependencies (those sneak up on you too and prevent perhaps a library upgrade that would benefit the rest of the app)