If Backblaze added simple, cheap functions-as-a-service, I'd switch everything away from the Big Three cloud providers and Auth0 except for fallback microservices. The biggest reason is bandwidth costs, which are disproportionately huge for small and medium businesses if there are more than a couple kilobytes of transfer per invocation.
That said, I am not super impressed by these first two compute providers, and probably would not trust them to give me enough nines even if they started doing FaaS. I can spin up something similar with Kubernetes on Hetzner for considerably less money...