Have you meet a cat? If they could talk it would be like talking to a spoiled todler. They will only do what they want and make a scene if you don't do what they want right now! I think it would be worst for the humas. I know my life would be (more) ruled by my cats.
Why would they have to? It's not like they need food, clothes, or shelter, they know how to sustain themselves without the help of money when it comes to those things. Besides, they already serve a good role.
Yes. Loud, egotistic and obnoxious when in their comfort zone. Disappears in blink of an eye when shit hits the fan. Got several colleagues like that. Wouldn't know the difference.
There are cities in Scandinavia who've set up vending machines where crows can deposit a cigarette butt to get a food pellet. That's a little like giving them a job.
We all like to joke about cats leeching but they're definitely not Capitalist. They're hunter gatherers for whom the concept of hoarding resources doesn't exist. To them, when there's plenty, you vie for it all within the social group (seems there are hierarchies?) and no one has to go hungry and there's no waste (including wasted energy). This also preserves plenty of leisure and social time.
If raised in an environment where it makes sense to hunt and you encourage them to do so, they'll happily contribute what they believe to be palatable food. If left alone, reasonably fit cats can fend for themselves too if necessary.
They'll take what shelter they get and bury their waste so it can fertilize the ground.
I've thought about this for dogs. I've never had a cat, but some of this probably applies, with the complication that they have a somewhat sour temperament as well.
It'd be nice on one hand, because I could say "chocolate will kill you, don't eat it", and they would know I'm not just being a chocolate-hoarding bastard. On the other hand, they couldn't get away with pooping in front of everybody. They get leeway on things like that because of what they don't know. It seems like a slippery slope where, yes, they would end up being treated more like older human children or human adults, and maybe that would spoil the cuteness a bit.
It's worth noting, I think, that historically dogs were expected to work for the most part. When food is often scarce having an extra mouth to feed for fun is conspicuous consumption. Often dogs were the food, too - we're the weird ones eating pigs but never contemplating eating dogs.