You are not safe from a colleague adding a dozen classes to add two numbers if you are enabling the "clean" crowd either. When I was at uni I was obsessed with these clean ideas and how they would allow big teams to work. after years of working I have seen these ideas fail to actually make teams work in an harmonious manner, worst hit I have experienced against these ideologies was finally working in a place without them and seeing how a lot of the alleged "advantages" of "clean code" could be achieved by other simpler means and how much in the way these ideologies are of actually being productive.

Productivity is achieved in spite of clean, not thanks to it.