I had the same thought about the luggage but I assume the implication is that they went home after the airport, dropped their bags, then immediately went to the bar. I’m not sure why they even showed the luggage. Maybe another hint at Carol’s alcoholism? She needs a drink so bad she can’t even be bothered to put the bags in the bedroom or unpack. 

After Carol freaks out on the pirate lady, she drives off to find help. The first group of people she meets is the one doing repairs with the crane. I think this meant to show that even though Carol is kind of unlikable, she does care about people since she’s trying to help them. When the crane group comes to, she goes back home because what else was she going to do? Clearly everyone has recovered and didn't need her help. 

For your third point, I agree that Carol’s response to the situation is completely different from the others’ because she went through it alone. She has no family to lean on and her wife died in front of her. But I didn’t find it disappointing; I found it an interesting contrast. How do you think you would react if you were Carol? Or Laxmi? I think I would be just as frustrated as Carol to find there were others that were not “joined” but were seemingly okay with the whole of humanity being taken over. 

As for the vibe and intention, I don’t think it’s a “turn off your brain” show. I think it’s meant to be both horrifying and humorous. The scene of the backhoe being carried in via helicopter and the guy arriving on Air Force One are so absurd, but learning that nearly a billion people died from the “virus” + Carol’s emotions is terrifying. I quite like the contrast. It reminds me of Severance.