Owing almost entirely to improved healthcare, improved infrastructure, and expanded relief efforts-- which we would still have in a world that was developing with cleaner energy.
That's debatable - it really depends on how much faith you have in technology.
For instance, improved infrastructure. Where do you think stuff like concrete comes from? Renewables are great for electricity generation, de-carbonizing industry/infrastructure is much more difficult. Stuff like expanded infrastructure, quick travel, satellite warning systems...fossil fuels made that possible, much as I hate to say it.
Yep. Again, owing to factors that we'd have regardless of our attachment to fossil fuels. Areas that suffer the most from climate change-- the global south, and urban areas blighted by smog-- have lower life expectancy than the global average as a direct result.
There's a reason I worded it originally as I did: "too soon was over a century ago". Even in my own preferred counterfactual, I was looking to a world in which the Industrial Revolution did occur. I'm envisaging a world in which we transferred in the century since.
Again, sure, but I'm not even sure if that's possible. On one hand, renewables have indeed been held back by the fossil fuel industry (and nuclear as well), on the other, the drop in renewables' cost is a very recent development. I'd love a world where we started transitioning to renewables as soon as we knew about climate change (which was the late 19th century), I'm not sure how feasible it is. But even then, fossil fuels have still helped human wellbeing. They're not the only thing (e.g. health), but the trend between energy use and human wellbeing has been linear until relatively recently.
By any measure, we as a species on average are doing better now than almost any period in history, I do get that. But vast swathes of the world don't experience any significantly improved quality of life as a result: billions continue to live in poverty (with poverty actually increasing in sub-Saharan Africa), and wealth inequality is worse today than it has been for centuries. And these are the places worst affected by climate change. So while the benefits are reaped by the global North, the dangers are experienced by the global South. We're not all in this together.
Well, yes, I agree, the global South is being hit harder than the global North. As for wealth inequality, you might be understating it (I don't think it's ever been higher in human history), though the current trends are that wealth inequality is decreasing between countries, while increasing within countries. And yes, poverty did increase fairly recently thanks to Covid, but the overall trend of poverty is down, globally.
And the world as a whole is doing worse to fuel that comfort: the rate of species extinction is sky-high, as well as the rate of deforestation.
Species extinction, yep, deforestation is another matter. Though since you and tstorm have commented on it, what's been left out is that even if the rate of reforestation/aforestation is greater than deforestation, deforestation arguably matters more as:
a) Older trees take in more carbon than newer trees.
b) Deforestation is highest in the tropics, where the greatest amount of biodiversity is - we lose more from deforestation in the Amazon than, say, Europe, for instance (I hate to play that game, but it's the game we have to.)
c) Afforestation doesn't help biodiversity since monocultures are just that - monocultures. It's true that the amount of greenery has increased over Earth, but new forests, plantations or otherwise, aren't as healthy/biodiverse as old growth forests/rainforests.