An author wrote this about Design Review:
It’s useless when 80% is about praising the design and 20% is about challenging the design.
It is unfortunate that this author does not understand the difference between Design Review and Design Critique. While the goal of Design Critique is to evaluate and improve design ideas, the goal of Design Review is to evaluate a product and service design objectively from different aspects and perspectives against a set of requirements and metrics. The goal of Design Review is not to improve the design.
Needless to say, it is a blatantly misleading and baseless assumption to use the percentages of 80% and 20% to contrast praising with challenging design ideas in Design Review. In Design Review, you are expected to be critical and objective in evaluating product and service design against requirements and metrics, not to challenge them.
Different from Design Review, in Design Critique you are encouraged to think creatively and critically, ask a lot of WHYs, identify design directions, identify design changes, encourage alternative and disruptive design ideas, apply user research insights, adjust metrics, and sprinkle tons of other things you can think of.
If you need to challenge a design idea, please challenge it 100% with a clear conscience that you are doing your best to bring your creative and critical thinking to the table supported by data and facts. If you think a design idea is good, praise it 100% and tell why you think it is a good idea. There is no need to limit your creativity to 80% and mix it with pantry politics.
In any case, talk to your users, listen and observe how your users use your products and services. Formally, test your design ideas with your users before any Design Review or Critique session. They are your best bet for an effective Design Critique and Review session. No design politics is required. Support good design ideas in a formal session, not in the pantry.