I don't know that it's a single big thing; it is indeed many small things that we have to manage ourselves. We backup the databases with our own scripts, we failover manually (I miss RDS), we use an overlay network because no VPC, and deployments involve ansible running docker-compose. There's basically no elasticity; we provision massive bare metal servers with fixed memory and disk installed. But, it is dirt cheap, so we manage, and all the pieces are small and easy enough to use.