i got invited to a club in my high school as a digital artist but the problem is that my art style isn't the art style that they were looking for and i'm struggling to adapt to the style they want me to make. it's like being asked to draw someone BUT IN ANOTHER ARTIST'S STYLE. am i being ungrateful if I back out or refuse the invite?

there's nothing wrong and harm of trying even if you fail. it's pretty good for your experience. go for it!