I like how you know that some classes are too big to manage. You list several considerations a teacher may use to determine what is and isn't a manageable class size. Then you turn around and use that to argue AGAINST class size limits.
You apparently oppose any class size limit because "it doesn't perfectly resolve every situation", leaving the teachers with no class size limits and no tools to resolve the very real issue of managing large class sizes.
This is a perfect encapsulation of conservative logic.
1.You see a problem you agree is real 2. You see someone's proposed imperfect solution to the problem which certainly would shrink the size of the problem but not perfectly solve it. 3. You oppose the solution because although it would shrink the size of the problem, it's imperfect and doesn't solve the whole thing all at once. 4. You don't propose or support any replacement. 5. The problem continues to grow unresolved, and you're satisfied having done a good job stopping any kind of progress whatsoever.