There's posers in all activities. I skateboarded for many, many years (contests, etc.) and it was about progression... not about cool, kit, and cred... it was about moving the sport forward, trick wise, if you were really into it. Sounds to me that you think both of these, skateboarding and street photography, are fads? Maybe they were / are the wrong activities for you?
The fact is that you don't have to be good to enjoy yourself and that is why you will always see what you deem to be garbage. Additionally, the internet has allowed us to see everyone's unedited photos. In the past, you would have had to go to the photographers house to see that. If you don't like it, ignore it. If you don't go to flickr, instagram, or tumblr, you won't encounter this type of photography.
What I don't seem to understand is how people can think photography (street or otherwise), which is simply one of the mediums used to document our times, can be dead? It's just another moment in time and it'll be documented just like the 1970s, 1950s, and 1930s were. I think the problem starts when people yearn to make 1950s style photos in 2013. Too bad, but cellphones are a part of our times and will be in the photos from this time period.
If you look at the history of photography, many themes are repeated...many great photographers have photographed the same things.