Grad dress confusion

Hey guys so graduation is coming up and I bought a dress. My mom and I loved it. We’re not the best financially but we got it due to grad approaching. Anyways I got home and my dad and brother completely disagreed. My brother said “omggg you were supposed to get something formal that’s not gonna work” and my dad said “that’s it?..... you went out just for that?” Basically idk if I should wear the dress to grad anymore. I’m sure it’s for prom but I really loved it. I don’t want to disappoint my mom and waste such a dress but I’m having doubts. So I wanted to know do you guys think my dress is wrong for grad?