You are talking about individual benefits. I am talking about the entire humanity. Cancerous cells also benefit from having their kill switches deactivated. They just happen to kill the system that they are a part of while optimizing for their own survival. I am making the point that selfishly wishing to live forever is exactly like that.
You aren't making that point so much as asserting it without evidence. There is no reason to think longer lived humans will contribute to extinction. Perhaps thousand year old scientists and economists will figure out solutions to humanity-threatening issues that would have gone undiscovered and longevity will, therefore, save rather than doom humanity.
Just because you can imagine that, but not really articulate how, longevity might be bad for humanity doesn't mean you've made an argument.
