This is not what a doomer is. A doomer is not a nihilist. A doomer is someone who recognizes a great threat of impending doom. They may raise the alarm bell in response. If they choose to lie down and wait to get run over, that's a nihilist doomer.
Fatalist might be a better word choice than nihilist. Nihilism is about whether meaning exists, but a lack of inherent meaning doesn't imply a lack of action. If you choose to just let something happen to you because you believe it's unavoidable then you're a fatalist.
