The side plot was to have Finn grow from someone with a good heart but nervous about his own safety into a true selfless hero. The fact it didn’t succeed just adds to the overall movie’s message that success comes out of repeated failure. If Finn’s mission had succeeded then the Resistance’s remnants would have slunk away without notice by the rest of the galaxy when they simply knocked out the tracker and warped out. Instead, a First Order Dreadnought was destroyed in a noble sacrifice and Luke’s reappearance reignites hope in the Resistance.
Leia having force powers makes sense. She was Luke’s twin and while she never had the time to properly develop them, both Luke, Anakin and Rey showed that even untrained individuals can wield tremendous power. I do think that scene was wasted as they should have had Admiral Ackbar be the sacrifice rather than a nube and it would have been better if she lifted rubble to save herself than just fly through space. But I was fine with it.
And what do you mean no one liners? The movie was littered with them.
Luke Skywalker: Where are you from?
Rey: Nowhere.
Luke Skywalker: Nobody is from nowhere.
Rey: Jakku.
Luke Skywalker: Yeah, that's pretty much nowhere.
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Poe Dameron: Permission to hop in an X-Wing and blow something up?
Leia Organa: Permission granted.
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[R2-D2 beeps]
Luke Skywalker: Hey, sacred planet, watch the language!
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Leia Organa: [to Luke] I know what you're gonna say. I changed my hair.
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Leia Organa: Wipe that nervous expression off your face, Threepio.
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Poe Dameron: You must have a thousand questions.
Finn: Where's Rey?
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General Hux: This is General Hux of the First Order. The Republic is no more. Your fleet are Rebel scum and war criminals. Tell your precious princess there will be no terms, there will be no surrender...
Poe Dameron: Hi, I'm holding for General Hux.
General Hux: This is Hux. You and your friends are doomed. We will wipe your filth from the galaxy.
Poe Dameron: Okay. I'll hold.
General Hux: Hello?
Poe Dameron: Hello? Yup, I'm still here.
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