I think this is true for 99% of conferences if we include non-technical conferences, making almost all of them a waste of time outside outside of the networking/hiring stuff.

However I will make a plug that the AI community has very informative conferences with proceedings and poster sessions at NeurIPS, AAAI, CVPR etc... all presenting new SOTA to the community.

I'd say it's similar with Chaos Congress and DEFCON, though perhaps to a slightly lesser extent.