That doesn't sound like a shift of work. It sounds like work I already would have done - performance tuning doesn't go away by bringing things in house.
Now that person I pay to operate the service can focus on tuning, not backups and other work that's been automated away.
It does make performance tuning harder since you likely don't have access to the codebase of the managed service, requiring more trial-and-error or just asking someone on the support team ($$)
Now that person I pay to operate the service can focus on tuning, not backups and other work that's been automated away.
Sounds like a massive win to me.