Can you elaborate on that?
[1] https://blog.cloudflare.com/incident-report-on-memory-leak-c...
This makes CF seem fine for your different variants of popcorn.gif, your (subresource integrity checked) Javascript implementation of the VIC-20 computer, or a public blog post, and NOT so great for patient access to histology results, private web forums, banking, and many other things on the Web.
1) Injecting themselves on the application layer (the current model)
2) Injecting themselves on the network layer, passing through only encrypted traffic between the client and your servers
Not every feature they currently offer would still be possible in model #2, but most of them (including DDOS protection) can still work in a limited fashion.