Is this necessarily true? At this point, I would figure that people who continue to publish on Twitter are aware of its restrictions and continue to communicate there with that knowledge. If anything, one could argue that trying to access Twitter content without an account is what's actually inappropriate here, as posters can no longer trust the guarantees of the platform.
> Twitter is supposed to be a website where people can share ideas.
Twitter used to be a website where people can share ideas. Twitter currently is a website where people can share ideas with other Twitter users. If you post on Twitter now with the intention of being truly public on the internet, I'd say you're using the wrong tool for the job. Whether that's a good business decision or not is irrelevant; the fact is that Twitter has changed its purpose, and users should update their expectations accordingly, however they see fit.
Your point about other users potentially not understanding the change is well-taken, and some of the other comments in this thread prove it (like a city's police department communicating exclusively via Twitter), but trying to make an open platform out of one that's fundamentally not (anymore, at least) seems like the wrong way to solve the problem.
People that create twitter accounts do so because they want reach. They want to be able to publish freely, to the internet, to share ideas, information they have, memes, whatever. But now, their reach is limited to other twitter accounts. Their voice is no longer public on the internet.
Twitter has some inertia that will carry this new model for now, there's a lot of twitter accounts, so many that most people won't know the difference at first. But as time goes on and people want to make things public and people slowly stop posting twitter links everywhere because they're useless (only useful to people with twitter accounts, so why share them outside of twitter in the first place) and every reference to something on twitter becomes a screenshot, people will look for alternatives to broadcast their thoughts.
Twitter is supposed to be a website where people can share ideas. You need an account to share ofc, but it's still supposed to be a website, you go there and read things. That's not possible anymore. Reading what someone has to say is only "using it" in the most tenuous sense. Using twitter is posting to it. People being able to read what you say is the whole point. They think they're forcing the whole world to get twitter accounts, but what they're really doing is forcing twitter users to share their ideas in more than one place, it's not going to turn out good for the company in the long run.