A dispirited shapeshifter's struggle to use his power for good intensifies when he's captured by a tight-knit, manipulative group whose members share the same power, and have their own twisted ideas about how to use it.

“Shapeshifter” is an archetype, a metaphorical function. It isn’t a character we can visualise as the protagonist. So what does this character look like?

“to use his power for good”: we assume this is the case for any kind of hero or superhero. They all use their power for good, so it is not giving us any information that is specific to your story.

“Struggle intensifies”: again, this is common to ALL STORIES.

So all we really learn that is useful is this: the hero is captured by a group. What sort of group? I have no idea. They share the same power, but what is this? What does the group look like, what unites them?

This logline is super vague.

You really need to start from scratch. Read the HOW TO WRITE section, read a few successful loglines and post a new version below in a comment.

Good luck!