I have been saying this for years. I made a ton of posts about it. I don't think they are going to fix it (I'm not complaining). I had to remove all the visibility fields on all the apps except for the timeline app. Everything except the timeline needs to be shared as public only. That is the only way to get rid of " Access Denied" blocks.

I think someone can use the developer app to create custom code so only items with certain visibility show up in the block, but I don't know how to do it. Also, a developer can create custom blocks from scratch.