In my mind, the argument for rebuilding the Federation would be better if we got some time to see that everything had descended into a crapsack galaxy without its presence. IMHO the first episode didn't quite cut it.
Really though, I don't know if I like the implication of a fallen Federation meaning a crapsack galaxy. I can absolutely believe that if most interstellar travel ended the Federation would start spinning apart. But everything getting awful in the absence of the Federation implies that its not moral self-advancement that made the Federation work, but a set of strong institutions providing stability. This is a remarkably conservative - even a reactionary - framing - that people are basically good not because they are enlightened, but because the state controls their behavior (even if the "stick" is very small).