Yep, then we'll ask AGI how to solve our problems, and it will tell us that we're screwed.
That would really be peak humanity.
My hope is that AGI effectively kills scarcity and therefore capitalism, and without capitalist pressures, I think a global transition away from fossil fuels entirely will be pretty easy
In some parts of the world, we have already reached that stage. For example in the US, everyone has enough food, energy and entertainment. But guess what is one of the biggest source of discontent? Housing, which is indirectly tied to land via zoning laws. Capitalism or AGI cannot really solve the problem of limited desirable land and politics, unfortunately.
I suspect most people already know the answer to how to live sustainably, it's just people don't like the answer. They know they'll have to consoom less and sacrifice some modern comforts. But who wants to do that? Who wants to disadvantage themselves like that? You first, right?
Not to mention some comforts are virtually necessities, like cars.