It is easy for classes to become boring. You can avoid this through a variety of methods, but one would be to plan for the flow of the class period so that the same teaching approach is not being used continuously.
For instance, a 60-minute class period can be broken up into three parts. The professor can lecture during the first part, the students participate in some kind of activity or discussion for the second part, and a summary or preparation for a project can take place during the third part.
For a critique, the first half of the class period can be spent by having small groups creating written evaluations of other students’ work, while the last half of the period can be spent addressing any questions or specific feedback that students wish to have about their work.