Also, somebody explain this to me. Am I dumb, or was Finn and Rose's entire arc completely pointless and only made things worse for the rebels? If purple hair would have just told everyone they were going to head to the base planet instead of being cagey the whole time, Poe would've never sent them away and never picked up Benicio del Toro, who promptly ratted out the escape shuttles. Why did that whole plan have to stay a secret?
So, I've seen this critique fielded a lot and here's my take on it at least. Please keep in mind that I've only seen the movie once, so there's a high probability that I've missed or forgotten something about this particular arc.
Regarding Rose and Finn's trip, I don't think it was inherently pointless as at least as far as the characters knew, it was one of the only options they had to get out of a "no-win scenario". We as the audience later learn that Laura Dern's plan had a point outside of "I dunno lets just keep going till we run out of fuel lol" and this is around the same time that Finn et al. do too. So while their plan ultimately failed, they were doing something they likely knew wouldn't succeed, failed, but were saved by the overarching plan they weren't aware of.
This plan is yet another explanation of Poe's character flaw: immaturity. He lacks trust and is unwilling to put his life in the hands of someone else who, as we hear him mention briefly, has some level of significant experience (when they announce she's taking over he talks about something she did.) And due to this he puts Finn and Rose in danger because it's a plan he knows rather than one he doesn't.
Now, I won't disagree with you that Laura Dern should have told Poe and all the Rebels her plan. I could also tell you a whole bunch of made up, editorialized reasons like she thought people might defect to save themselves, maybe thought there were spies on board, maybe just hated Poe, etc. to justify it. But at the end of the day it really isn't covered well and while I have my thematic interpretation of it, I fully understand why people have gripes with it.