Speaking for myself, I am not concerned how others dress. It's a personal choice and it says something about one who does not dress appropriately and in a decent manor. Everything is subjective. My view of casual/informal is different than someone else's. I can only be responsible for my attire.

If you don't want to be with "slobs," then leave the "slobs" be. The majority will be dressed in an appropriate manner.

No matter which cruise line you sail on, or where you go in the world, there will be those who simply don't care about dressing nicely. It's all a personal choice and everyone is entitled to that. Their vacation, their choice. I don't focus on this at all. I focus on my vacation and my choices.