Yes, it will help you to cover cases like where the server phyically explodes, but that's basically irrelevant, most problems where you need a DBA are caused either by data corruption caused by application code or developer, or performance issues caused by DB structure - in those cases the cloud platform won't do anything for you, they just host the server. They can restore backups, do monitoring and tune the server, not your particular app/db structure - but all the big problems are there.
"most problems where you need a DBA are caused either by data corruption caused by application code or developer, or performance issues caused by DB structure"
Is running Mongo going to solve any of those problems?
Without a rigidly enforced schema I would guess those problems are going to be amplified rather than solved.
Yes, it will help you to cover cases like where the server phyically explodes, but that's basically irrelevant, most problems where you need a DBA are caused either by data corruption caused by application code or developer, or performance issues caused by DB structure - in those cases the cloud platform won't do anything for you, they just host the server. They can restore backups, do monitoring and tune the server, not your particular app/db structure - but all the big problems are there.