Is development really important?

MOST DEFINATELY!
The difference between someone who's been developed and someone undeveloped is very significant. When your developed you will have a better understanding of how you receive communications via your psychic senses and also which senses your working with, if undeveloped you won't understand as much and you may even misunderstand and miss some of the communication or if you misunderstand you may give the total wrong information. Also if undeveloped you may mistakenly claim to be a medium when really working psychically. 
​personal development is also an integral part of becoming a "better you" or opening to spirit
So for me, development is important for mediums, psychics and all lightworkers.