Don't consider your results and the fact that you didn't make it to eliminations as a failure. You guys should continue on the same path and keep improving as you did over the past three years
The fact that you guys had a Dean's List in 2013 accounts for the incredible team you guys are!
That being said, I would revise the thinking behind this year's design. Your robot was built for catching, but it didn't effectively and reliably catch truss shots from alliance partners. Add that to the facts that it was a very high robot - the higher it is, the easier it is to tip and fall since the center of gravity is so high - and that the picker wasn't consistent and reliable enough: I can't speak for all but that would be the main points that might explain why other teams didn't invite you on their alliance.
The key to success is to focus on what yields the most results according to the limitations you have, work with it and make something simple, reliable and consistent enough. If you need more details, don't hesitate to PM me.