Spiritual development is the process of becoming fit for a higher level in the spirit world. There are three areas of spiritual learning: skills, beliefs, and evolution.
Spiritual Skills include the ability to serve as a conduit for spiritual healing and the ability to perceive communications from spirits. However, having these abilities does not indicate that someone is advanced spiritually.
Beliefs are what you believe about the afterlife and the purpose of the earth life. That is also not related to how spiritually evolved a person is.
Evolution is primarily what spiritual development is concerned with. An highly evolved spirit might incarnate without manifesting spiritual beliefs or skills. The process of spiritual evolution involves the development of personality traits of a highly evolved spirit. These traits include the ability to love and absence of selfishness. However, spirits incarnate for many different purposes and it is not really possible to identify who among us is advanced spiritually and who is not. Therefore it is unwise to judge other people based on whether you think they are spiritually advanced or not.