After Suzie's computer wizardry, they exited to house to find Eden (Suzie's sister) in the van making out with Argyle, but the girls did not leave with them.One thing that was immediately apparent to me, and then immediately forgotten, was that Dusty's girlfriend and older sister were in the van one min, and then just gone the next. Did I miss something?
Answer to the spoilerBut the biggest flaw for me was:
Their plan didn't work. I get that they're saving Vecna for Season 5 or whatever, but that was a lot of watching time to invest in a plan that failed. Especially since everyone worked so hard and sacrificed so much! It really felt like a DM who had a villain they really loved, so even when the characters were smart and lucky, they refused to let the villain die. It left a sour taste in my mouth.
I guess it just was not successfully sold to me as such, especially becauseAnswer to the spoiler
But, fundamentally, they weren't lucky. Their luck was hosed by outside actors - the (psycho) army guys who thought Eleven was the threat to Hawkins and then Jason "I'm gonna grow up into a smarmy televangelist" Carver at the house. That's not the characters being lucky - that's the characters being unlucky. The lucky part is they did as much as they did while (mostly) surviving. This is The Empire Strikes Back/Goblet of Fire moment for the Stranger Things cast.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.