Polling is incredibly unreliable. That is people that pick up the phone and talk to pollsters. Do you know anyone under 60 who does that? Additionally, a lot of those calls are on landlines. How many people do you know who have landlines? How many of those are under 60? The polls are heavily skewed towards boomers.

All these incorrect assumptions of yours could have been answered simply by actually reading the poll report before making claims about it:

On June 28, 2024, Data for Progress conducted a survey of 1,011 U.S. likely voters nationally using web panel respondents.

https://www.filesforprogress.org/datasets/2024/6/dfp_post_first_presidential_debate.pdf

Literally entirely online.

Polling has long since shifted away from relying on landline cold-calls. And I agree that now is certainly sub-optimal for a change; that should have happened during the Primary (you know, where candidates present themselves to voters to find out who voters want), rather than the DNC pressuring other democrats out of running. But better late than never.

In the end, you and I are probably never going to see eye-to-eye, because of one fundamental difference of beliefs; you believe Biden might win. I don't.

Since it seems clear that Biden isn't going to step aside, I really hope you're right and I'm wrong, but I'm not banking on it.