The dress code psa

I read posts on here about putting dress codes on invitations, and people against it. I read about using invitations to judge formality, and people debating it. Here is what happened to me on Friday. I got an invitation that read very casual to me: looked like a chalkboard, mason jars, etc. I planned what I thought I would wear. The DAY OF the wedding, I got on their wedding website to verify the church info, and it said Dress code: Formal. I had to change my outfit with 3 hours to go, but it was fine. I had something I could wear for a formal wedding. FH just changed to wearing his full suit. No big deal. As we arrived at the wedding, we see people standing outside the church, chatting. People in khaki pants and sneakers, women in capris and flip flops, short sundresses and sandals, and I was confused. I looked at the website again, and it definitely said formal. I was at the right church. I assumed these guests didn't see the formal dress code, or just didn't care. We get inside and the ceremony starts. The wedding party is wearing dress pants with no jacket, the BMs are in short, casual dresses. FH and I are dressed more formally than the wedding party, minus the bride. She was in a gorgeous, elaborate ballgown. I spent the entire night feeling out of place, but at least FH could take off his jacket. I wish I had followed my instincts with the invitation and worn my original dress. I honestly don't know where the disconnect was, if I thought differently of formal than they did or if they assumed since she was wearing a very formal gown that it made it a formal wedding? It was a fun wedding, and I had a great time, but it was NOT formal. Please, please, please, don't tell your guests how to dress. Even with this "formal dress code", it showed that we all had VERY different ideas about what that meant because even the bridal party wasn't dressed formally.