These are technical in nature, but further demonstrate the need for humility and caution in making consequential business recommendations from conjoint research. Discrete choice experiments offer an improvement with respect to all five of these problems with conjoint analysis. The respondent's task, though still artificial, is closer to what consumers do in real life which is to make choices. If desired, different alternatives may be described by different ranges of variables. In fact, they may be described by different attributes.
Consumers appear to be able to handle a larger number of attributes in discrete choice tasks.
There are also techniques for simplifying the presentation of alternatives, such as only displaying attributes in which the alternatives differ. That's real life. Statistical difficulties do not go away, but concerns over degrees of freedom are rarely present.