Gould and Buchanan seem to be adopting Engels especially for their science fights.
The problem with capitalism is that it has been adopted all over the world. Once ingrained systemically, the transition to alternatives seems like a bit of fantasy.
I recognize that it is but one ideology, and yet its pervasiveness and ability to adapt and encumber resistant movements make it all the more formidable. Capitalism seems better able to accommodate a critique of metaphysics in the wake of Marx.
Again, the most well-known Neo-Marxist theorists have pushed Marxist thought into our century, and yet they recognize the dominance of the capitalist model as being so pervasive not because it's the better one (necessarily), but because of its evident entrenchment. That doesn't mean there aren't other models out there, communal, etc. It just means that those models are, for all purposes, impractical at the moment, and any chance they have of becoming dominant is usually rooted in the complete collapse and total failure of capitalism. Which won't do much for the proletariat, I suppose.
The biggest obstacle for alternative views is the "self-interest" of leading industrial and political classes, I think. They pushing forward this libertarism as de facto social legitimation. The power-holding classes made quite a progress in the recent decade in accumulating a critical mass of economic and political power. By now they are almost autonomous from the masses (and any "dangerous" ideas).
Several aspects of ideological isolation dynamics can be found in Naomi Klein's book "The shock doctrine". I will give two examples from there:
If you look at late capitalism today, especially it's global character, the dismantling of this system would cause such upheaval, especially when it comes to distribution of energy resources and food, that many hundreds of millions would die, if not billions.
It's so systemically entrenched at a global level that a move to another system is the equivalent of radiation therapy to remove a cancer.
Here and there, there may be alternative models, but globally it seems to be the model most countries have adopted.
This global capitalism is a problem, in all its unsustainability. The world we know is dismantling before our eyes.
It's the end of the world as we know it, and I feel fine...
I am not talking about imposing other global order. I do not recommend any particular global order at all. In contrary - global top-to-down economic solutions must be resisted. To survive this economic crash, every country, community must have freedom to make decisions of its own. Someone would strike then ingenious solutions very probably. That's why plurality of ideologies is welcome now.
I wish this capitalism to retain most of its structure and buzzing network as it can. But the global system must be open to voluntary unscripted adaptations of its parts. What is not welcome is to let clubs of G20-lite leaders of wealth and power holders to decide everything. That would likely to lead to reversing all social evolution of the last 120 years, back to "Oliver Twist" scale gaps between haves and havenots.