As the non-custodial parent, my answer presumes that the child or children will not be moving with you out of state. From a practical standpoint, moving out of state obviously presents the problem of you having less time here in Michigan to be with your child and with probably less time to be with the child due to school schedules and the child's ability to travel. To that extent, your ex-spouse is correct.
However, depending upon what your previous arrangement for custody and parenting time are, you should still be able to maintain your relationship with your child through custody and parenting time. A motion with the court can be made to change the custody and parenting time to appropriately reflect the change to your situation. Finally, if you plan to move the child's residence out of the state of Michigan, you must seek approval of the court by way of a motion to the court.