I'm not entirely sure if those candidate can be considered "far left," whatever that means these days. Certainly not Dukakis. As governor of Massachusetts, he's mostly known for being fiscally responsible but mostly hands-off regarding social issues.
But, that aside, what Bernie and AOC bring to the party is an emphasis on working class and labor issues, and that is a direction the party needs to go in. I don't agree with those who claim the party shouldn't address issues related to trans and LGBT people, since they need representation too, and they're certainly not gonna get it from the GOP. But bread and butter, working class issues need to be a stronger focus within the party, including promotion of legislation that supports workers and middle class Americans. Too much focus does go to headline-grabbing issues and feckless displays against Donald Trump, and less for actual governing and protection of the middle class and other people who work for a living. I think AOC especially understands these issues, and, perhaps with more experience in government, can one day become a real, strong force for working class people.
That's my hope, anyway.
-- A2SG, as I've often said, if there's one thing the Democratic party excels at, it's disappointing its members....