I wouldn't know for sure what you should do about your psychiatrist, but please don't fall into the trap of thinking everything is meaningless and just brain chemistry, that life is pointless. Everything is affected or caused by brain chemistry, but that doesn't mean it's meaningless.

I remember having such thoughts after experiencing the extreme contrast between discovering a reality where everything's extremely meaningful and a reality where everything seems arbitrary (the one we too often live in anyway). Reality is all fiction and one isn't more true than the other. Some you might share with others. None of it is pointless.

Most if not all religions and all true religion is based on one reality some have been lucky enough to experience. It's not arbitrary. Specific teachings may be misguided but they're based on a universal truth. Religious people may make grave mistakes, but certainly not all of them do.

There's truth at the core of all delusions. The mistakes are made when interpreting and expressing them. But still they may convey some truth. They may resonate and inspire.

You should maybe just respect his beliefs and don't base what you think of him on prejudice.