I've checked in a few places, and I don't know that Smil does break down plastics usage to the extent you'd like. And that's a fair gripe.

But, again, his principle audience, as I take it are those who like the modern world, and would like it to continue as it is, with minimal change.

And to them he's pointing out the underlying costs and necessary conditions (including, as you'd likely characterise it, vast overconsumption of plastics), and their implications. A visceral knowledge of which is lacking in far too many people.

Smil addresses this in his book's introduction: the unprecedented, if uneven, wealth of the post-WWII era, the expansion of human understanding and fact that it's escaped the grasp of any one person --- the Renaissance Man --- centuries ago, and both a fracturing and failure of knowledge even amongst elites (political, commercial, cultural, scientific, ...) to the extent that at best even amongst the elites knowlege tends strongly to the superficial. (There's an excellent interview by Edward Murrow of Robert Oppenheimer in which the physicist notes that everyone, even scientists, are amateurs outside their own very narrow fields.)

Your principle complaint with Smil seems to be that he didn't write the book you wish he had. And to that extent I'd say you're right, he did not.

But he did write the book he felt the world needed, and which he set out to write. And I think he's correct in his first assessment and largely successful in the task. Whether either of those are sufficient is of course another matter.

The message you seem to be taking away is that Smil is arguing fossil fuels are necessary and will continue to be necessary. There, I think you're wrong.

One tactic critics of environmentalists and sustainability proponants have long used is to point out all the wonderful things fossil fuels have done for humanity, with the obvious conclusion that therefor we must continue to use them. I could point to specific examples from Milton Friedman, Julian Simon, and numerous speakers and writers from the Heritage Foundation, Heartland Foundation, Cato Institution, Adam Smith Institute, Fraser Institute, and others (most part of the Libertarian, and heavily oil-industry funded, Atlas Network).

But that's not Smil.

At the conclusion of his chapter on energy, and discussing decarbonisation, Smil writes:

What we need is to pursue a steady reduction of our dependence on the energies that made the modern world. We still do not mnow most of the particulars of this coming transition, but one thing remains certain: it will not be (it cannot be) a sudden abandonment of fossil carbon, nor even its rapid demise --- but rather its gradual decline.

That paragraph cites his own earlier writings on energy transitions.

Again: Smil is addressing both denial (that the transition doesn't need to occur, that climate change isn't real), and wishful thinking about the ease of such transitions. This is a field I've watched for nearly fifty years, and even worked in to some extent (not deeply, though putting me in touch with some key people and organisations). And ... there's been a lot less progress than I'd have hoped to see. It would have been much easier to get started earlier, and it's going to be much more painful.

If I've one disagreement with Smil, it's that the transition might be rapid. But the cost of that would be that it would also be highly traumatic. To the tune of billions of deaths and centuries of hardship. Possibly worse.