Castform is my favorite pokemon and I really want to make it work but it’s so bad in masterball looking for advice

I’m currently in masterball for doubles and I really want to make castform work. It just feels so horrible. I was trying to do a Mega Charizard Y and Mega Frosslass team and just using castform to counter fire types or water types depending on which mega I bring but that doesn’t work too well. Has anyone had success with castform? Please help I love castform so much.