Yeah, cloud providers do advertise DBaaS as 'simple' but there's a reason they don't advertise anything on parameter tuning or say that they replace DBAs [1]. You pay them so that they give you a self-managed database, but they definitely leave a lot of work on your plate.

RL-based tuning might change that soon though: https://github.com/cmu-db/ottertune

[1] https://aws.amazon.com/blogs/database/part-1-role-of-the-dba...