It's like you are deliberately misunderstanding. Degrowth is the voluntary, ethical managed reduction in consumption and people. Saying "Thanos snap", tells me you don't know what you or I am talking about.

There are a million important conversations to have about consumption and its distribution, they are just of a secondary order to solving the problem. Yes billionaires on private jets should not exist. But ~8.2 billion let's say for simplicity's sake, lower middle class (I'm assuming here your goal is not to maximize people at the expense of abject poverty and primitivity) are not going to fit in their environments in any environmentally sustainable fashion. It absolutely must be both population and consumption. You don't realize how far over the line we've gone.

The extact numbers depend on the details, but 1 billion mostly vegetarian humans living mostly in efficient urban centres defined by electrified economies, public transit, passivehouse can keep a modicum of techno-industrial civilization like modern medicine and probably not cross any planetary boundaries and can rewild much of the planet so the biodiversity loss gets plugged.

8.27 Billion poor humans you suggest, will collapse on their agricultural needs alone. The exhausted groundwater, soil depletion, chemical loading and transportation let alone the floods, droughts, and other extreme weather exacerbated by climate change will exceed earth's carrying capacity in many respects, let alone all the other consumption for human life that goes with those numbers.

Edit:

My point is simple: anyone who believes that climate change is solved by depopulation is dead wrong.

Fine. But that is not what I was ever talking about. Climate Change is one small facet of sustainability. Degrowth is about dealing with all the planetary boundaries we've crossed. Sustainability is all factors combined. Land use, soils, pollution, biodiversity, all of it.

Edit 2: Here is a thought experiment to illustrate. How many people do you think we can clothe sustainably? All our polyester, nylon, rayon clothing is shedding microplastics into the environment. You are full of them now. Fibres are shed each time your clothes go in the wash. So the sustainable solution is to use decomposable materials only. Mostly cotton, linen, hemp and wool. How many people do you think you can clothe with global production of just those materials, without synthetics? How much cotton can we reliable grow every year, accounting for floods and droughts etc...

In a sustainable world, are you still wearing your synthetic Nike Air Force 1's, or are you wearing leather shoes with leather soles? How many cows and sheep are you growing for those shoes? On what land, with what feed. Where do you put the cows emissions?

Tackling sustainability is an enormous job. Solutions are often difficult and limited and imperfect. But every single solution gets magnified and multiplied by having fewer people.

Collapsing birth rates, as required by degrowth are a big part of that solution.