There is no "the Left". Even in the US alone, that label covers a
huge range of independent groups, whose ideological views are pretty wildly different on most topics, with only some very vague shared principles. The idea that "the Left" is some homogenous hive mind is ridiculous as hell.
That doesn't make it "too spread out ideologically", it means that your insistence that they're a single entity is
wrong.
Also, the "progressive stack" isn't really a "thing". It's a weird concept that basically only ever existed briefly in the Occupy movement, but for some reason, you folks think it's some kind of core left-wing concept, and it's not. It's a pretty damn silly idea.
As for the identity v. economy nonsense, the Democratic platform in the 2016 election had a
huge focus on economic issues;
https://www.democrats.org/party-platform
Just going by section titles, the first three major sections are entirely about economics. It wasn't "abandoned" in favor of "identity politics", it just didn't get
media attention because there was nothing to get angry about, unlike racists who get enraged by "identity politics".
And I'm going to keep putting "identity politics" in quotes, because the
reality is that it basically boils down to "we respect civil rights of all people and think prejudice and hatred over variety is wrong". Which isn't really something you can take issue with, which is why you want a convenient label to use.