Understandability of your communication and documentation is prerequisite for acceptance!

Understandable diagrams contain 5-15 elements with their relationships - normal people simply cannot grasp more than that number.

If you have overloaded or large diagrams, reduce the number of elements by abstraction:

• Aggregate several elements into a named blackbox. These elements should be cohesive, they should somehow belong together. The criteria should be an explicit decision.
• Refrain from showing loads of details, e.g. attributes or methods of single classes. Those details can often be left to source code.
• Especially in runtime scenarios, don’t always start with the beginning of a scenario, but dive-right-into the interesting parts.