Honestly, I'm not straw manning deliberately. I absolutely accept that I have only a superficial understanding of the ins and outs of open source.
I wonder if I could ask some questions to clarify things, because I am genuinely here to learn, and change my mind if necessary.
Referring to open source applications:
Why should they not? An open option does not mean you can't make proprietary software, and it does not imply that money cannot be made.
So how does that work in practice? Imagine I come up with a great new concept for working on ODF files; I recruit 20 programmers and we spend a year developing this new application. I've had to borrow money to pay the programmers, but the investor was OK about it because he was expecting to see a lot of sales, which will give a great return on the investment.
If I open source this software, others can pick it up, change the splash screen, and put it out there free of charge. They can do that because they didn’t have to pay anyone to write the software. So when it's out there free of charge, why would anyone pay for it? How does the original investor get his money back?
You don't have to open source everything you develop. Nobody is arguing you should. You're strawmanning desperately.
No, not desperately. Not even deliberately.
There is plenty of money to be made, for those who consider that the only reason to do anything - and there are reasons beyond money.
I've got all the usual open source applications on my Mint installation, including LibreOffice. I didn't pay for them. I don't pay to use them, so nobody is making any money from me. So how is the "plenty of money" actually made?
The success of open source development is behind almost every service and piece of software you use every day, including proprietary ones. Even if you want to retroactively limit that sentence to 'for desktop application development', you must consider that said open source desktop software, hardly having failed, is in routine use by those developers and many users, and actively encourages proprietary tooling to make itself worthwhile.
I'm sorry, I was actually thinking of Linux desktop programs. I can imagine that all those Linux servers in the cloud have all sorts of specialised programs to provide the functionality and management tools they require. And I can see the end users paying money to the software developers for maintenance contracts.
Where I'm stuck is when it comes to people like me. Even if LibreOffice (say) is widely used by companies and individuals, they haven't paid for the privilege, and certainly they won't be paying for a support contract because LibreOffice doesn't need support: everyone knows how to use it.
These are genuine questions, not challenges. I have no interest in arguing, except to repeat one last point. When I say "open source doesn't work" it's because I look at the big applications in the Linux desktop world and - in my judgement - they really are old-fashioned, ugly, klunky, with steep learning curves and obscure workflows. It seems to me they don't get the level of attention from their developers that Windows apps do.