Many of the arguments made here (not all, but that's a separate argument: "but this other argument would still stand" is not a valid defense of a poor argument and it is important to whittle the set down to the ones that are actually strong) are the same arguments people make against private communication technology.

So, yes: it is more efficient to not have to encrypt everything, and yes: it is more difficult to deal with spam when everything is encrypted, and yes: building a system that is decentralized is hard, and yes: anything you build that is decentralized can be built more easily and maybe even more "safely"--for even an actually-reasonable definition of "safe"--by some centralized entity, and yes: a fully decentralized and private communication platform would absolutely be used by at least some terrible actors to accomplish terrible things that might be made more difficult if that platform did not exist...

...but, no: just because something is more expensive or more difficult to pull off doesn't mean it isn't worth the cost, and no: just because some terrible actors use a platform that doesn't justify taking it away from all users, and no: just because previous attempts at something have failed it should be illegal to attempt to pursue the technology.

If you make an argument that implies a kind of centralized control over things being good because privacy (which this article claims cryptocurrency provides--and it can, just not using Bitcoin--so if you want to quibble about that you are actually arguing against the authors of the article, not me, as many of their points seem to rely on this privacy at least mostly working) is an inherently dangerous thing to offer people, and when I call my bank there 100% should be a person there looking at my billing history getting to judge me for the things I buy and the places I shop and what those things imply about my sexual orientation (maybe you see me going to a specific bar a lot) or the medical conditions I have (based on the medications I am buying or the clinics I visit)...

...well, I would then want you to look in a mirror and really ask yourself is that's the kind of person you want to be, as I am going to claim that privacy is a thing we need to be offering all users even if there are costs and to the extent to which the current banking system and financial system fails to operate if people are granted such privacy, that's on them, not on us. You can't sit around and claim that people should get to have end-to-end encrypted secure blinded "communication" with their physician and then simply refuse to blind all of the financial transactions that leak a lot of that same secret information.