I've seen enough concession politics and worker integration to capitalism to conclude that social democracy is not and will never be an ally to communists or even an actual leftist ideology. Rather, it's a tactic used by liberals to pacify the working class by getting the workers on their side, offer them concessions to make them live comfortably and thus integrate them into the capitalist system.
Another thing that came to my mind is the much less popular ideology known as democratic socialism, which many people don't bother to differentiate from social democracy. However, there are significant differences between the two.
1: Democratic socialists tend to emphasize the significance of the environment more than social democrats and often call themselves eco-socialists or the green left because of that.
2: while social democracy occupies historically rather popular social democratic parties, democratic socialism is a current found in various left parties. For example, Party of European Socialists being social democratic and Party of the European Left being democratic socialist.
3: they rely heavily on social groups perceived to be disempowered compared to their empowered counterparts. such as immigrants, non-whites, women, ethnic minorities, Muslims and other religious minorities and sexual and gender minorities, while the social democratic parties although they too rely somewhat on them still get mainly the worker vote unless it goes to the right-wing populist.
4: democratic socialists can be actually considered socialists at least somewhat, whereas social democrats cannot. This causes that due to the extensive propaganda campaign by anti-communists of which social democrats are a part of, socialism is given a bad name and thus democratic socialists, even though they're "democratic", suffer due to identifying as socialists and thus won't get the working people's vote.
This causes that they turn to the aforementioned social groups and away from the working class, the group the left is supposed to empower and whose rights it should uphold. As the democratic socialists seen as the left-wing does this, the left is seen abandoning the working class, providing ground for right-wing populists as not only do they present themselves as a workers' party but also the party of the social groups which are polar opposites to what the left party represents: whites, men, natives, Christians, heterosexuals and so on, parading them as "actually disempowered ones" due to the left's advocacy of affirmative action to their groups.
What needs to be done? What can be done? How can the left be made a true workers' movement again?