This is the only compromise I would accept, otherwise I'm in favor of E2E with no backdoors. People who care about preventing CSAM and prosecuting pedophiles should consider this an improvement over the status quo.

The UN security council is VERY effective at what it's actual purpose is, which is preventing all out nuclear war between the major super powers. That is why the confirmed nuclear powers are the only ones with veto powers (minus Pakistan/India/NK, interestingly).

Everything else is quite explicitly window dressing.

I’m unsure what you’re saying here, can you clarify?

Is it that Baseline seems overly bureaucratic and will be ineffective, or that people should not support any CSAM lists at all?

The UN security council is hardly a non-entity. They aren't great at addressing certain kinds of geopolitically contentious problems, but UN peacekeepers have 12 active deployments. (https://peacekeeping.un.org/en/where-we-operate)