Being devil's advocate here...
Without context it is not easy, but if I thought a trainee instructor's delivery was "boring" I wouldn't hesitate to tell them so, as part of a constructive critique. It wouldn't be doing them any favours to say their brief was wonderful if it actually had a lot of areas for improvement. A lot of trainees are VERY boring before they develop confidence and a "style" of their own. You are paying to learn, not to be flattered. You get out of it what you put in.
A lot of training instructors is role playing, think about it from that angle before you judge the CFI. Not all students are "nice" some of them are absolutely horrible! but you still have to get the job done. Comfort and cotton wool in the course won't do you any favours at all in preparing you for the "real" world. The best instructors I had sometimes left me feeling like cr@p and ready to quit, but then more determined to improve. The nicety-nice ones were so busy wanting to be liked they taught me next to nothing.
Enjoy your instructor course, it's the most fun training there is, and learn to gracefully accept criticism from your more experienced colleagues as a way to improve yourself. You will have to, until the day you are a CFI yourself. Good luck!