"Left" and "right" are relative terms, not absolute. Mainstream economic left is whatever the majority of people who are left of center hold to.

The economic left isn't allowed into the mainstream of politics.

"Left" is not a synonym for "socialism".

Socialism is a word that can be defined in absolute terms. But left/right is defined relative to society as a whole. Whoever is left of center in political mainstream is the economic left, by definition.

Seems like you're trying to define words in a way that makes the actual state of affairs in the USA impossible to describe.

No matter if all leftists are removed from society, leftism must still be said to be half of what remains.

Nothing in mainstream USA politics should be described as "economic left."