I'm starting to think that the reason egalitarian systems are failing to gain traction is because we spend too much time focusing on the scientific aspect of the creation of social systems while neglecting the utopian, fantastical, idealized side of it.
For a while now, Socialism no longer means a system (because, after all, "no one knows what it will look like") and it has become instead a codeword for a certain worldview regarding the malleability of the human spirit and the socio-historical conditioning of the social structures that surround us, and a general class attitude characterized by opposition to the projects of the bourgeoisie.
This is all fair and good, but I think that without a picture of what the endgoal is, these two are incomplete.
Let's take conservatism as a frame of reference of what a complete idea looks like. Conservatives have their worldview and they have their ethic, their values and collective attitude, but to complement this they have an utopian idea of the traditional society, free of corrupting influences: the traditional family, the two kids, the dog, the suburban house, the homogeny of ideas, the small property or business owner, the common moral code. A connective tissue between individuals made out of ideas, faith, respect. They create in people's mind a subconscious idea that many grow attached to, and trying to recreate this fictionalized lost past is a goal for many of them.
Fascists replace this by a more militarized version. Service, struggle, a certain degree of equality, the corny imperial-classical architecture, the statues extolling the athletic body, all that nonsense. Liberals, on the other hand, go for the multicultural, diverse, rational and secular universe, although they too suck at inciting people's imagination through imagery.
Now, I challenge you to think about what the Socialist horizon is. There isn't one. People have a fictionalized lost past to look for in conservative and reactionary ideas, and a slightly improved and more technocratic present to look for in centrist and progressive ideas, but they don't have an egalitarian future to think about. And before saying I'm full of shit, remember that Socialism was more popular when the egalitarian society was a common trope in science fiction.