In the blog state of open source, Prusa complains about cheap 1:1 clones who do not honor the open source ethos and as remedy suggests altering the license.

The most successful companies, e.g. Microsoft and Apple, in the world are closed source.
Still closed source seems not to work for a number of technologies; operating systems (Linux) and programming languages (Python).
In the nature of the firm, Coase argues that the main reason to establish a firm is to avoid some of the transaction costs of using the price mechanism.
Open source lowers the transaction costs for inbound innovation. Information is more readily available to outsiders and less asymmetric. As a result, the technology grows.
I think open-source is best suited for "highly" complex products with an initial weak product market fit. It works better for software than hardware. As hardware is harder to reproduce. This leaves the question of monetization.
Open source software is now monetized by cloud providers who earn money by running it in the cloud.
Examples are Github, Amazon Web Services or DataBricks.
It is also monetized by software developers who tailor the software for specific business needs.
They enjoy large benefits by the fact it is open source. As they can simple hop companies and sell the same knowledge again. A problem with proprietary software is that the new firm or client of the developer would also require a license.

In your blog you also give an example of solar panels. One example for all is solar panels – the original inventions and processes were gradually copied by Chinese companies. After that, with the help of state subsidies and tax breaks, they drove all competition out of the market within a few years. Today, you have virtually no chance of buying a non-Chinese-made solar panel.
I agree with your assessment that this makes solar panel manufacturing less profitable. It might also be a reason for a government to intervene using tariffs.
Still, an entrepreneur can still make money. Once the solar panel becomes free, the challenges becomes getting it on your roof. You might also need advice on how to best place your solar panel. It is very hard for the Chinese to compete with a Dutch solar installation company given the fact they are in China.
They can also not work in the Netherlands due to regulations.  If China makes printers for free, you might need to alter your workforce or firm. I still see a lot of ways of making money.

Moving back to the Prusa firm. I would not alter your open source approach but better look at how it can provide unique value. Your company actually pursues a mixed strategy. Part is closed and part is open.
It is impossible to make a firm a completely "open".  I would not focus on changing the relation between Europe and China or the patent system. These things are external to your company and not under your control.
You can make it easier for external parties to add new tools to your printer.
You could give these external parties a slice of the profit.  Goal here is to really think outside of the box and look at your relation with the customer.
As example, there is a Dutch company called Swapfiets, who offers bikes via a subscription service instead of selling them. This has been hugely successful. I would not advice you to offer a subscription service. Still, it shows that the way you interact with the external parties can be a key differentiator.
If you control the most popular design of the printer, you should still be able to make money simply as you decide which parts end up in the next printer.
A successful open source approach, requires more thought than simply putting the source code on the web.
This was done by Lulzbot and not successful.

Finally, I partly disagree with your view on patents.
I believe like you and the Economist that the patent system is broken.  From experience, I believe that most patent applications are a failure.
Still, you should patent given the opportunity. If you have a lot of money, understand the boundaries of your innovation, have a good patent able innovation; you should patent. A patent might also be key in getting government support.
In your case, you might not want to use your name as it destroys your image.
You could still use a shell company and someone else his/her name.  Some companies hide patents so they can strike their opponent by surprise. I currently lack the resources to do it.
Filing patents is also very tricky.
Still, I don't see how not patenting helps the world if you really see a good opportunity. If you want to change it, complain about it, use the power you have in a way which aligns with your views, but don't leave money or power on the table.