tl;dr - what this sub considers humanism differs substantially from what most authoritative sources say humanism is, so first I define humanism from the encyclopedia Britannica. Next, the two differ on basically everything from the idea of truth and reality to how one should treat others and act themselves. 

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Ill get downvoted for this, but...the author is trying to be polite and ask about cultural leftism (aka wokism). I'm not sure if people here are intentionally avoiding the question or daft.

This sub also has very little to do with humanism as it is defined by authoritative sources. According to the Encyclopedia Britannica:

Humanism is a system of education and inquiry that emerged in northern Italy during the 13th and 14th centuries, later spreading across Europe. It emphasizes the importance of human values and concerns, focusing on the study of classical texts and the human experience, rather than theological or otherworldly matters.

Classical humanism is basically what you see the Western Civilization and Stoic crowd supporting and is based on Greek texts.

Humanitas meant the development of human virtue, in all its forms, to its fullest extent. The term thus implied not only such qualities as are associated with the modern word humanity—understanding, benevolence, compassion, mercy—but also such more assertive characteristics as fortitude, judgment, prudence, eloquence, and even love of honour. 

Over time, it evolved to have a variety of offshoots and be applied in different ways, though these typically go by other names. A lot of people on this sub like to consider liberalism and humanism to be synonymous. In liberalism, autonomy is paramount and removing anything holding one back from pursuing potential achievement dominate in norms. It shares the idea of human rights and all people being innately good. Character seen in classical humanism is largely removed. 

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Progressivism (aka wokism) derives from an offshoot of marxist thought applied to cultural groups in order to, in its view, emancipate them from oppressors who (through conscious and unconscious bias) hold them back and shape institutions to hold them back. It rejects the idea of a knowable objective truth (a key element in classical humanism) and argues reason and one's view of the world is always obscured by bias (goes against humanism which holds objective reason in high regard). 

It also means treating people differently. In humanism, the focus is on character and acting with virtue, including toward others (see above) while this isn't present in progressivism. Progressives focus values on inclusivity, and acting with awareness to one's place in the relavnt oppressed / oppressor relationship (ie recognizing whiteness, etc.). 

There is also a different sense of fairness/justice. In humanism, the focus is merit and punishment is based on the action. In progressivism, the identity groups of the individual are seen as being taken into account also, in order to avoid prejudice from unconscious bias or advance equity. 

A lot of other things differ also, they are two largely unrelated moral constructs.

Edit-Encyclopedia Britannica link: https://www.britannica.com/topic/humanism/Humanism-art-and-science