While it is true that first impressions are the most important, if your message is strong enough and you convey it in an intelligent, informed way, then you stand a much better chance of being taken seriously. We all strive for respect in our own way, so if you look less than traditional, make sure you can back up your point.
Yes, we are too hung up on what people are wearing these days. Clothing is a protection against the weather and a covering for private parts of our body we choose to cover--neither purpose anything to get excited about. Clothing is also a personal statement of who an individual is. With as many different people as we have on this planet, there is no way everyone can dress alike--nor should they.
Many people get upset over what people where nowadays which is a little absurd. Every generation had their group of people who complained about the way people dressed. The people complaining typically turned out to be the older people of the time, while the crazy dressers were younger. Clothing changes over time just like people and civilizations do.
What an individual chooses to wear sums up many things about that person (ie what their current mood/state of mind might be, their expectations for the day, etc). In addition, it is the first piece of information that an individual can use to determine important possible things about someone else such as an individual in a business suit would not normally be assumed to be a street thug. Appearance is by no means the only factor to be used in assessing a person, but it is certainly an important one.