I'm not going to fact-check this article for obvious reasons, but is this article referring to actual CSAM or drawn artwork? The author seems to be heavily implying the former but I suspect it's actually the latter.

The article cites the second and third ranked instances as the most active instances and prevalent CP communities, but both are japanese so I'm going to guess it's mostly drawn artwork.

The article is simply complete FUD

Like any distributed service, 'Mastodon' will have bad and illegal stuff on some server somewhere. However those instances will be blocked and defederated by any mainstream instance.

Using that as an excuse is like trying to justify banning access to the entire internet because of bad websites.

You could use the same arguments against the web.

It's bullshit fearmongering that uses the existence of a couple of heavily blocked instances to smear the thousands who have nothing to do with them other than using the same software.

Post is now accepting new users via a waitlist. It’s only a matter of time before it steals everyone worth stealing from Twitter.

I somewhat hope so but my personal preference is Mastodon. Journalists are one of the larger demographics for Twitter so I think it's smart in theory that Post targets them. Twitter's draw was the flow of information like a crowdsourced newswire, so it'll fail in "stealing" journalists until it "steals" others.

TL;DR Less of a foregone conclusion than you say.