Saying "your car has a flat tire" isn't blaming your car, and saying "Mastodon has a CSAM problem" isn't blaming Mastodon.

This article seems to do a pretty fair job of pointing out that they investigate this issue on many platforms, but that they've seen higher rates of CSAM on Mastodon than others. They also specifically call out, accurately, that decentralized platforms have different challenges with addressing these problems when compared to a platform with a central arbiter.