No one is entitled to much in life. But people expect many things which they aren't entitled to. This is normal, and does not mean there's something functionally wrong with people that expect certain things.
I expect my neighbor to not flip me off every morning. Am I entitled to it? No, not really. Being an asshole is not illegal. But I would probably still complain about it. Does that make me entitled?
What you need to do is manage expectations. Which... this is one way to do it.
Expectations can be set by the license, most of which used for open source explicitly outline that the author is under no obligations.
There's quite a distance between your example and the behavior of most open source developers. Are you implying that those who don't respond to suggestions are flipping you off?
It's clearly arguing that we expect many things that we have no right to. Open source developers aren't bound by any expectations that we have of them, but we also have no duty or obligation not to have expectations.
My 2ยข is that some open source maintainers have severe boundary issues that are pretty natural for people to have. They need to be liked by everyone, which is probably why they decided to do OSS, because if you give people things for free, they like you.
People's expectations rise to the challenge and demand the maximum amount of free stuff, and the maintainer is pushed to their limits to satisfy them for little or no renumeration. But if they stop, people won't like them, and that sets off some useful animal heuristic where that possibility causes them to feel in actual danger (which they may project onto the project i.e. "the project is being endangered by entitled users asking for things.") The loss of what you think people love you for (giving away free shit) is a loss of identity and one's place in the world.
The reaction of the demanding users is just as natural. Remember: if you feed a stray dog, people don't naturally feel the dog is now obligated to you, they feel that you are now obligated to the dog.
You have to be modern, establish boundaries, and not place enough of yourself in the expectations of other people that they can destroy you with disappointment.
It might be better to move to proprietary or Free software. With Free software, you're establishing something and granting it to the public (not becoming something), and you can walk into and out of it with no feeling of guilt or of being taken advantage of. No one else will get rich off your work, and if your work helps people it will live forever. With proprietary software, you're dealing with safe, formalized purchase and support relationships. It's this OSS shit that seems to drive everyone crazy.
You speculate too far. One may wish to share their work for many motivations aside from needing to be liked. A gift is best given with no expectation of reciprocation.
Open source has a definition, but some movements have saddled it with additional expectations. Disappointment can arise from malformed expectations. When that happens there are a few options. One can avoid disappointment by seeking new labels when existing ones are compromised. Or, one may recognize this subversion as a power play and challenge it. The latter path sometimes doesn't end well.
Whichever path is taken, I agree that the objective should be in establishing boundaries. The author of the article achieved that, at some cost.
I expect my neighbor to not flip me off every morning. Am I entitled to it? No, not really. Being an asshole is not illegal. But I would probably still complain about it. Does that make me entitled?
What you need to do is manage expectations. Which... this is one way to do it.