By contrast, 1→2 billion took 123 years (1804–1927), according to the estimates of at [1], though Wikipedia suggests that data prior to the 20th century may be unreliable.
[1]: https://en.wikipedia.org/wiki/World_population_milestones
But when you actually examine what a demographic collapse on a grand scale could look like - it's possible that this amount to the kind of suffering that we haven't seen in a century. There's no way to know, because it's uncharted territory, but the potential downside seems huge.
"maybe lower the population a little" - some societies will have some gradual reduction in population. Many countries are already or will soon have their populations of young people decline drastically. Our societies are pretty fragile systems, and when you change the ratio of young to old at the rate we're going to, it's hard to anticipate how these systems will cope.
This does not happen without population growth.
You also saw the quality of life of the average person also more than double.
Even if you expect it from bacteria, you imply it a bad because bacteria? What sort of logic is this? Should humanity stop doing anything it sees other forms of life it does not view favorably doing? If so. You go first… let’s start with breathing.
What happens to bacteria in a sealed system? The population grows until it hits carrying capacity, then drops precipitously once resources run out. That doesn't sound like the ideal model for society to adopt.
But beyond that you forget how big the earth is, not to mention the billions of habitual planets humans one day will call home (although net might not call them humans, but who knows)