Corporations are just a vehicle for organizing work and profit around a venture. There are many other ways to organize work that have nothing to do with corporations or unions. Consider partnerships, sole proprietorships, cottage industries, co-ops, and more specific arrangements within those vehicles like profit sharing, limited partnerships, and employee ownership (not to be confused with stocks/options, though they are similar in concept).
Capitalism can take many forms, and not all of them require we turn the way we organize work and wealth generation into a zero-sum game between entrepreneurs and laborers. It's just the first thing we've found that's worked out in the environments it's been attempted in. I think there's room for businesses and economies to try out novel models for organizing work, and I suspect many of them could get us better or more efficient trade-offs between profit, productivity, and general welfare for all parties involved.
None of those have proven to work at scale though. So as far as we know corporations is how you have to do it. You can believe that there are other ways, but you cannot know that there are other ways as nothing else has proven to work.
[0] https://www.mittelstandsbund.de/themen/internationalisierung...
In the US, we have:
1. A poor social net, meaning employers need to take on the onus of providing many basic benefits like health care.
2. A political environment that conflates communism/socialism/collectivism, which really muddies the waters around organizations that aren't hierarchical.
3. A work culture that prizes profits over all else. Orgs do not have to be this way, and if you look at expectations/obligations of similar entities in other countries they're expected to balance profitability with things like social welfare.
I think you're right in that within the US, corporations have shown the best ability to scale, but I believe this is a consequence of the economic/regulatory/political environment of the US than inherent superiority of corporate governance.
This is a very subjective conclusion that is likely very dependent on what economic class you fall into. Many folks on HN (myself included) fall into the category white collar or professional workers. For many other parts of the labor market, you're literally trading sweat and toil for money.
Add to this that labor intensive jobs tend to lead to a lot of physical wear and tear with less medical benefits than white collar professionals typically receive, then just by quality of life and welfare alone most people doing physical labor would come to opposite conclusions re: pro union vs pro cooperation economic/governmental policies.