Identifying leftism as a harmful ideology is certainly a critical step, however it's very difficult to gain traction with that because the term "leftism" is very, very close to "left wing politics", which is strongly normalised as being entirely acceptable in civilised society and always has been since the start of modern democracy itself.
Indeed if you try and figure out where the line is between leftism and left wing politics, it rapidly becomes very difficult. Left wing political parties at least in the Anglosphere are all fully on board with this new leftism of racism, hatred of Anglo culture and history, and all that comes with it. To take a stand in e.g. the workplace against leftism by arguing it is an intolerant and hateful ideology is equivalent to arguing that all left wing voters are supporters of intolerant and hateful ideology. But many of them are not fully on board with all that stuff, even though their chosen representatives are, so to make progress here requires a way to distinguish between people who vote left because they want a higher minimum wage or something like that (reasonable, not the enemy), and people who vote left because they want statues to all be abolished, conservatives to be driven underground and white people turned into second class citizens in their own countries.
That in turn would require consensus around a term that describes the former, socially acceptable state of left wing politics: back when it was a sort of pro-big-government, pro-regulation, primarily economic belief system. Debates about economics and the role of government are far less fraught and far more intellectual than debates about the intrinsic worth of people based on gender or race, so splitting the left cleanly into the parts that want such debate and the parts that want ideological attacks and no-platforming seems like a necessary first step.
Unfortunately whilst there is an abundance of words to describe the new left wing politics (woke, wokeism, leftism, identity politics, critical theory, neo-Marxism, "anti-racism", third wave feminism etc) there aren't many terms which clearly describe the old left wing politics. Thus the traditional wings get pulled along by the new strains, as they lack the intellectual and linguistic framework to push back or separate themselves from the parasitical takeover of their institutions.
Interestingly, Europe seems to have less of a problem with that. In Europe it's still common to describe the more classical centrist positions as "social democracy". This phrase is is widely understood to mean classical left wing politics focused on economics, welfare, higher taxes etc, but without the overt focus on race and gender.