I think you underestimate how reduction in complexity can increase reliability. becoming a sysadmin for a single inexpensive server instance carries almost the same operational burden as operating an unavoidably very complicated cluster using a cloud provider.
Nowhere near the same. Admining a few servers is far easier than a mix of AWS cloud services, especially when they are either metal as a service or plain VMs.
not if you are using Atlas. Its as simple as it can be with way more functionality you can ever admin in yourself.
As others have said unless the scale of the data is the issue, if your switching because of cost, perhaps you should be going back to your business model instead.
