Nothing. By definition, I'm already a "doomerist", I guess.

And it just becomes worse when one gets "transcendental". While everything you listed ("Climate changes, rise of far-right ideologies, erosion of democracy, huge setbacks in human rights, rise of bigotry and hate crimes, destruction and loss of biodiversity, criminalization of activism/union strikes, etc") is enough to get a "doomerist" framework and existential dread, wait until you catch yourself gazing into the depths of the cosmic abyss, expanding from mundane events to atemporal, ineffable cosmic noumena, and realizing that everything was just the tip of a gigantic, Lovecraftian-like iceberg.

Cosmos's indifferent to us. A supernova could explode within our galactic vicinity and vaporize the Earth in just a blink of our eyes, for example. Earth will be engulfed by a bigger Sun (Red Giant) in the future. Every living being, including us, is walking on a "thin" plaque floating above an enormous ocean of deep magma (ever thought of Pacific Ocean as being so enormous? Well, it's nothing in volume compared to Earth's magma).

This, my friend, is a stage of "doomerism" which I can't describe how deep it is compared to the known "doomerism".

Technically, I consider myself a nihilist, as the way I conceptualize things relates to nihilism (and, etymologically, I'm a "Nihil"-centered person, I sort of worship the "Nihil" a.k.a. the nothingness, so I'd be considered as a Nihil-ist). I'm not exactly Nietzschean because I never dived myself into Nietzschean books, although I like some of his quotes (the gaze into the abyss, for example). I'm just "nihilist" as in "there's nothing: literally only The Nothing is".