[zv]

Gated automated deployment (for MSSQL - dacpac via Azure DevOps, similar things exist for other DBs). Usually can be pre-tested if prod db copy is restored on lower environments. If anything, rollback can be made to previous deployment.

Either way, you need to designate someone who is knowledgeable to oversee the process. Automated deployment just makes this process way faster (thus "reducing bottleneck") where this person only needs to review code to see if anything suspicious isn't there and approve the deployment.

Manual deployments are prone to human error, especially under stress/time pressure. If manual deployment "package" (a set of sql scripts) is poorly written, there's huge incentive to "contact directly", which again could lead to manual errors.

The biggest drawback is culture which is the hardest ("we done this way for n years and we don't want to change").