The point was to break the chain of star wars trope - 2-3 guys break into evil guys base and save universe by themselves. They went on this crazy mission they were told not to and effed everything up instead of saving everyone. Everyone in the theater expected it to work because it always works - the fact that it failed spectacularly made it fun, and taught Poe a lesson.
As for Rose, I don't get all the hate. She was fine. Not great, but not this target of disdain that she's becoming.
I think we know why she is the target of disdain.