I honestly think a one- or two-server setup with scripted server re-creation, proven in Vagrant or whatever, and maybe using Docker but only to isolate services

I honestly think a one- or two-server setup with scripted server re-creation, proven in Vagrant or whatever, and maybe using Docker but only to isolate services on those one or two servers and make it easier to re-create, tested frequently by spinning up local dev copies, and (obviously) with backups, is probably a stabler, cheaper, and higher-availability set-up for the vast majority of use cases. Even if predicted, scheduled downtime is somewhat higher, it's probably worth it for the many benefits. But no, cloud everything.