I'l make it short: the script is the foundation, without a good one you can't build anything solid but also just because you have a nice one doesn't mean the end result will be good, that all depends on what you build on top of it ( storyboarding,chara design,animation,OST,backround art,voice acting,photography etc....)
Also want to mention that a script is different from dialogue , Paperman most definitely has a script, or to take another example
the illusionist has almost no dialogue but it has a script (sidenote: I hate it when trailers for "foreign films" throw in a gazillion critic quotes).