I'm currently on tchncs. As said in my last paragraph, that while I understand this doesn't reflect on all servers, rooms, and spaces, it still makes me wonder if I should be using a protocol where the official space for it ran by the foundation building the protocol has such ineffective moderation to the extent that CSAM can exist in their biggest official room for multiple hours.
To give a comparison, let's take Tor. Tor is used for people to stay anonymous online. Now this of course is a bit of a double-edged sword since on the one hand, you have the intended purpose where people utilize it to circumvent censorship or just as a method to increase their privacy in their daily browsing habits. The other side is people who use it to access and distribute illegal services or content such as buying and selling drugs, or distributing and viewing CSAM.
Now do I feel uncomfortable utilizing Tor because I see them as not doing enough to prevent the bad people from being on their network? Of course not, there's a lot of great people who use the network from hobbyist projects to simply enhancing people's privacy. However, if the Tor project had an onion site directly administered by them that constantly had moderation issues with CSAM or illegal services, then I would be more likely to utilize something like I2P because I wouldn't be comfortable utilizing a service where the developing organization didn't properly moderate that stuff on their own onion site.
That's the case with Matrix. I'm not even quite expecting them to be on top of everything sent to their server immediately, but this was the biggest room in their official space, and it becomes a question of whether I'd be comfortable using a protocol where the foundation behind it's development doesn't take adequate action dealing with CSAM in their own rooms.