Ending poverty is a purely mechanical problem, with very straightforward solutions if you have robots that can do any mechanical task. You don't need to give anyone a job, you just need to give them food and shelter. (Ideally also medicine, but it sounds like that part at least he's thinking about, although again, perhaps not for anyone who doesn't already have it.)

Curing diseases and making people feel fulfilled are great goals, but they're not the primary ones in my mind. They are in Gates' mind because those are the biggest challenges he has personally experienced in his life.

Making the structural changes to our economy should be trivial if AI works as well as he's supposing it will. We won't need an economy at all, not to solve the problems caused by unemployment. (And that's the thing, is unemployment is not the actual problem, it is a cause of problems, but AGI would give us easy alternatives to the fundamentally unattainable goal of full employment.)