It's not just about wether a machine can do something better than a human. Firstly you need to account for costs. If a machine can do it perfectly, but a human can do it 80% as well for 40% the cost, the human still has a job. The cost to hire the human is heavily tied to the economy and their cost to live, which actually ties back in to how expensive/accessible things are. You'll notice that there's still a lot of manual assembly in manufacturing today for this reason. Secondly there are a massive number of social issues. When a person does something wrong it's a mistake, when a machine does something wrong it's broken/unreliable/unsafe. So it can't just do something better than a human, it has to do it exponentially better and much cheaper(including maintenance/development/switching costs).

Maybe that's possible, but this blossoming we have as AI today is nothing like that. Knowing how we do AI today and the fundamental difference between general purpose AI, which is very stupid, and extremely specialized AI, which is very smart but only useful for very specific things, gives me zero confidence that the recent AI developments are headed towards an AI that's cheaper/smarter at everything than your average joe.

Take a look at all the voice assistants. They're very good at some specific tasks(they aren't general purpose, and they fail at super basic things. These failures can be addressed, but Siri isn't going to learn them on it's own, some one needs to program new features still. As an example, say my wife name is Jane, and there's another Jane in my address book. If I asked a human assistant to call Jane and let her know I had a meeting and I'd be home late, and they said "Do you mean Jane Doe or Jane Smith?", or forced me to say "tell my wife" otherwise she wouldn't do it, I'd fire her. The human assistant understands that "home" is where I live, and the only person who would care when I got home named Jane is my wife. Also when they called my wife and my wife asked when I would get home, they would think to check my calendar for the meeting I had mentioned in the message, if it was there tell her how long the meeting ran, and then even people able to figure out that there'd be some transit time. They might even think to ask wether or not I was going to grab something to eat before I got home since they might know that sometimes when I stay late I get a sandwich at the cafeteria and that my wife doesn't need to wait for me to have dinner.

Identifying that "text" means send an SMS, and that the next could words need to be searched in my phone book, and the remainder is the message, is not general purpose AI. It's some voice recognition with some fuzzy matching and is not that far off from SmarterChild. All the connections a human assistant can intuitively figure out in todays "AI" need to be programmed in. They need to know to look for those variables, and make relations between them. If we stop developing Siri, she will never learn on her own to make those connections or look at those variables.

Finally, the idea that if machines can do everything we do today, there will be nothing left to do is the definition of the lump of labour fallacy. Just like everything else with technology in the past, reducing the cost to produce X increase the availability and accessibility of X, reducing the number of people who had to work on X, and allowing people to instead start working on new things Y, or to do interesting awesome things with X that weren't possible when X was scarce, creating industry Z.

Unless once AI is invented there is literally nothing else new we can create, I think we're okay. And I don't think AI will be out-inventing or out-creating human beings in me or my great grand kids lifetime. There's just no precedent I can see that this is happening.

tl;dr: our AI suck, AI will make things(and subsequently labor) cheaper, AI will enable us to focus on new things, AI will create new industries of jobs.