I don't think agents are obsolete by any means. In fact Disney actively promotes independent agency to become Disney "authorized", or whatever term they use. You are right though, making reservations through Disney is as easy as logging onto a computer or calling a phone number. I prefer using agents such as Magical Journeys (there are many others out there, some that sponsor this board).
It cost you nothing to use an agent, all pricing is set by Disney. What I like is that once I make a reservation the agent continues to work on my behalf by monitoring specials and discounts and applying them to my reservation as they occur. It saves me from calling back to Disney or having to constantly track things myself. I also had a situation where I had made a future reservation on a
Disney cruise. I then authorized Magical Journeys to take over managing the reservation. While reviewing the reservation Nancy pointed out that there was a room with a veranda available for less money then our inside stateroom and got us moved. This was not pointed out to me when I made the initial reservation with Disney. This is just one example. There have been many times where Nancy has found us a campsite at Ft Wilderness when Disney was sold out or rooms at resorts when all were sold out.
My point here is to consider using agents. They bring much more to the table than just being an"order taker". The good ones really work for you!