Why is it misguided? You can improve your privacy using it as a mixer vs. not coinjoining at all. I don't think you have to believe you're achieving perfect privacy.
The example above is extreme and users don't have to completely merge all their UTXOs after the coinjoin.
They are misguided because the problem is not to obtain a reasonable anonymity set but maintaining your wallet's privacy. The only way to achieve that is by managing your UTXOs and revealing as little about your wallet as possible with each transaction. That's something that coinjoins cannot help you with alone. The only way to do that is with a tool like Wasabi and a decent understanding of how it works.
I know the example is extreme; in fact, I was the one who said it was an extreme example. But the point is that they do that because they cannot see how their wallet's privacy plummets after each of those transactions. With Wasabi, they would have noticed it.
