Why does AWS give me a critical security alert if I have a public bucket?

I have a few public buckets meant for serving images. AWS is saying general purpose buckets should block all public read access.

I'm not sure why they would allow buckets to be public if they do not want people to make public buckets.

If so, what settings do I need to adjust on my buckets to make this alert go away, or do I really need to serve static images through some other method?