Why Stalin was not simply a hands-off wartime leader

Was Stalin unlike Hitler because he left the fighting to professional generals?

No; Stalin also interfered and made major mistakes, although he may have listened slightly more than Hitler.

Stalin interfered extensively in military affairs and made major blunders. He may have been marginally more willing to listen than Hitler. The difference is one of degree rather than a division between professional delegation and personal meddling. This compact answer cautions against reducing a complicated command comparison to a simple binary.