This is nothing new. Statistically there has been a very quantifiable shift. Barack Obama was our last Presidential candidate to win the working class vote. We still have tons of working class voters, more than we have college educated, but Republicans have more.
Analysts look closely at the most accurate demographic information they can find, and they discuss it with Rho Khanna, Michael Bennett, Gavin Newsom, Chris Murphy, and anyone else who will listen, all the 28 hopefuls. Sanders doesn't need to be told, he knows these things in his bones.
If I can suggest one thing I'd suggest listening to David Shor's interview with Ezra Klein. Shor was an analyst for the Biden, then Harris campaign, he is a committed Democrat. Shor doesn't give bad news for fun, nor to cause despair, we need to get it together as a party. We'll win the midterms, we'll flip the house, but long term things look bad for the senate and the presidency, and the house during presidential years could be a problem.
We don't need to adopt more centrist positions, or more Republican positions, we need to go to where the American people are at.