Define "progressive," and explain why Harris, Newsome, Shapiro, and Whitman are not progressives.
That's a large topic to 'define'. The Democratic Party has two main factions, the Progressive faction and whatever you want to call the rest - centrist, corporatist. They differ on policies and priorities, though of course there is a good amount of overlap.
One way it's been described is that Republicans are the party of oligarchy, and the non-Progressive Democrats are 'oligarchy-lite'. To understand that needs understanding the situation in the country - how the country has been on the road to increasing oligarchy sinc Reagan, reaching new highs in inequality, and how Democrats have had modest reversals of bits of that but largely left Republican policies in place.
It needs recognizing that those Republican policies, mostly left in place by Democrats, have redistributed over $50 trillion to the very wealthy, and how only the Progressives are fighting for the solutions, while the other Democrats 'chip away' with much lesser policies.
For example, Bernie successfully got $10 trillion bill for the American people supported by Biden - and then the rest of the Democrats cut it down to under $1 trillion IIRC.
Progressives have 'the Progressive Caucus' in the House with close to 100 of the over 200 Democratic members. The policies, views and politics of the candidates I named are aligned with the non-Progressive Democrats - though they might try to claim the level when it's convenient like Hillary did. They will sometimes agree with a Progressive policy position, but that isn't enough to make them 'a Progressive'.
For example, when Biden agreed to Bernie's bill, it didn't make Biden 'a Progressive', though he deserves a lot of credit for at least initially supporting it.
He remains the president who also did all kinds of things at odds with Progressives. He didn't fight to undo, for example, trump's tax cuts, or to pass universal healthcare, or other policies. He remains the person who DEFEATED the actual Progressive in 2020, Bernie, leading to trump in 2024, uniting the non-Progressive Democrats.
I could go on, but as I said it's a very large topic to discuss the policy and political differences, which should be pretty clear. Review the Progressive Caucus policy and budget documents and compare them to the main party's. In short I'd say, the main party isn't fighting to reverse as much of the move to oligarchy as Progressives. They make much smaller changes, leaving great inequality.