Elected officials have significant influence they can bring to bear on specific decisions, general operations, and in many cases personnel decisions. That’s true at the level of individual house members and can be more true for other offices.
The rule of law and checks and balances also means these elected officeholders don’t have arbitrary control, which has a lot of upsides (and produced a professional and effective federal workforce) as well as some limits.
I swear we have a problem where we quantize to caricatures rather than recognizing tuned balance, and control theorists would probably anticipate this means things will start to swing a bit wildly.
Executive power over the civil service is an ant driving an elephant. You can say it's a good thing and it's intentional, but the fact of the matter is that the executive appoint a fraction of a percent of the positions and those positions have nominal personnel powers that they can't really use without fear of getting sued.