These are critics concerning how classes are chosen and used.
ArgoUML has the following critics in this category.
DataTypes are not full classes within UML 1.3. They can only have
enumeration literals as values, and only support
query
operations (that is operations that do not
change the DataType's state).
DataTypes cannot be associated with classes, unless the DataType is part of a composite (black diamond) aggregation. Such an association relects the tight binding of a collection of DataType instances to a class instance. In effect such a DataType is an attribute of the class with multiplicity.
Good OOA&D depends on careful choices about which entities to represent as full objects and which to represent as attributes of objects.
There are two options to fix this problem.
Replace the DataType with a full class.
or change the association aggregation to composite relationship at the DataType end.
Suggestion to improve readability by having fewer classes on a diagram. If one class diagram has too many classes it may become very difficult for humans to understand. Defining an understandable set of class diagrams is an important part of your design.