Leftism is, pretty much, utilitarianism - I mean, the idea that the fundamental aim of all public policy ought to be (in some - vague - sense):
1. The optimisation of human happiness and minimisation of suffering...
2. In a quantitative sense - with the assumption that it makes sense to summate happiness and suffering across groups...
3. In this world and during mortal life.
Thus - utilitarians include all mainstream politics of all parties and Western nations, all bureaucracy, all functional social systems (law, civil administration, health, education, police, military, mainstream churches...) and all the mass media
The implicit assumption of utilitarianism is therefore always and necessarily atheist, materialist, positivist, modern and Leftist - no matter what individuals may say about their personal religious or spiritual beliefs; or whether they may imagine themselves to be reactionaries or Right Wingers.
Modern utilitarianism is so pervasive that most people simply cannot envisage that most of the world and all societies in the past had transcendental goals - usually religious, or to do with concepts such as honour, the family, clan, tribe or nation; the land...
Many things - but a hedonic pleasure-pain quantitative calculus was never the bottom-line until modernity.
In modernity, utilitarianism is both the public ideology (what people ought to believe, according to mainstream propaganda) and the actuality (in the sense that other motivations are enfeebled and ineffectual).
Yet utilitarianism is demonstrably incapable of motivating a coherent society or human life - and instead there is a pervasive despair, self-hatred, and desire of self-annihilation.
Utilitarianism is, indeed, merely one-step away from nihilism - that is from the denial of reality; from the conviction that reality is-not-real.
By trying to base life on feelings, and by pretending that feelings can be meaningfully predicted, manipulated, measured and summated - utilitarianism has built modernity upon sheer incoherent nonsense: that is the foundation of everything.
In sum; utilitarianism is a false and deadly metaphysics - a set of nonsensical and wicked assumptions.
Unless or until we recognise this as a fact, and change it; we shall remain locked-onto the cultural destination of willed damnation.