A few questions,
1. Whats the ranking of your classmates like? If most of them are very low ranked that might be a reason why everything is static. If this is the case give it time and dynamics might come into play when their ukemi skills go up.
2. How long have been in this dojo? If you recently started (within a month) are they getting ready for test? They might be going test requirements to cram for a test. Again if this is the case give it time and see what happens after the test....
If neither of those answers helped, you need to decide what to do. Talk to the Sensei, be respectful but tell him how you feel. That way if you decide to leave he will know why. (common curtsy in my opinion.) Ask him if he will supervise your teaching of a more dynamic class. You're only a nikyu but you can always pass something on, and if he's supervising he'll be able to correct your mistakes
Just my 2 cents.