Not just that, but getting a deep understanding of how the RDBMS (or NoSQL solutions, for that matter) implements the database is important as well is very impo

Not just that, but getting a deep understanding of how the RDBMS (or NoSQL solutions, for that matter) implements the database is important as well is very important. It requires a low level understanding of how the implementations write things to disk, perform indexing, structure data in memory, and their characteristics when distributed to make truly informed, non-cargo-cult decisions about database technologies. Otherwise you're just shooting in the dark.