Google, Discord, and Reddit all take swift and decisive action against CSAM. I have never organically encountered CSAM on Google, and have only encountered it on Discord and Reddit because of deliberate bad actors. Outside of Reddit's early mistakes with /r/jailbait, none of these services end up being preferred by pedophile communities, because they can expect to be shut down quickly if they rally there.

Telegram has become a hotspot for CSAM to the point that it is pretty much inevitable that you're going to encounter someone peddling it just by browsing other channels.