What are the disadvantages of circuit training?

Muscles suffer.: Circuit training is the "jack of all trades" of the exercise world. You get aerobics and weight training, but not good versions of either. Usually the efficacy of the weight training suffers. Better to separate your cardio from your weight training; you'll benefit more from both that way.

None: It is excellent, if you include all the muscle groups. You can move at a rapid pace and get the HR up. Good to add some dedicated cardio before or after, or in between days. Good Luck.

Disadvantages are: specialized equipment, ample space and required health and safety monitoring. Of course the advantages overweight the disadvantages.