Cloudflare has both static hosting + CDN. There are dozens of CDNs and hundreds of static hosts that you could combine.

GCP, Azure also exist with similar solutions

I mean, whatever the problem with proprietary AWS, it seems like it would be the case with GCP, Azure, Cloudflare.

I don't really see the benefits of putting eggs in multiple baskets. If one basket is down (e.g. images) the site is practically down in many cases. Plus you have to deal with fragmented billing, etc.

How are Cloudflare, GCP and Azure any less proprietary than AWS?