Whenever I hear about how Democrats listened too much to the left, I think often about the Loan Shark Prevention Act I worked on that AOC and Bernie introduced into Congress. It would put a 15% cap on payday and credit card loans. When we polled it, it was hugely popular everywhere but especially in red and purple districts. But even faced with these facts, none of the more establishment Democrats wanted to sign on to it.
And now Trump is proposing a 10% cap on credit cards, and if he does it, it'll be a very popular win.
My take is the problem isn't that Democrats got too left. They are just too cowardly, and that cowardice defines too much of the party. When it was less cowardly to take an unpopular 'left' position, they did. But in the majority of cases where there is an option to do nothing with no political downside, the default very often is to do nothing because that is the 'safer' thing to do.