Old tech could work around these outages. Set up GSLB at a DNS provider that does health checks or perform your own health checks to both origin and CDN's and

Old tech could work around these outages. Set up GSLB at a DNS provider that does health checks or perform your own health checks to both origin and CDN's and use API's to change DNS. If the origin servers are OK and the CDN is not, automatically change DNS to a different CDN. There should be multiple probes that form a consensus. This process assumes one is managing the configurations of their CDN's through code and API so that one can set up and tear down any number of CDN's on a whim. That does mean having contracts with more than one CDN provider however the cost should be negotiated based on monthly volume. i.e. the CDN with the most uptime gets the most money. If an existing CDN under contract refuses to negotiate then move some non critical path services to them and let that contract expire. Instate a company wide policy to never return to a vendor if their contract was intentionally not renewed.