I agree. There are loads of dresses on that site that look really stunning. Personally I would go for one of the others which is a bit less bright, but that is down to the individual and knowing what works for you.
The original dress you posted is absolutely fine IMO. You need to look like you made an effort, the end, and you want it to be something you feel confident in which is best achieved by not asking the internet.
I cannot get on board with all the made up rules. Pick something and stop asking for opinions from people who don't know you, who won't be in the room and won't see the pictures. What you think is truly what matters here. When is the last time you heard a bride say the MOG's dress was too bright or too flouncy? I'm afraid I don't even remember what my mum wore to my wedding let alone my brother's.