I respect the passion for history, but the game can be mighty dull, unlike the tumultuous times it's simulating. Long stretches of waiting for number to go up. Repetitive, monotonous gameplay loops. Surprisingly limited bureaucratic, diplomatic, and economic options. Lacking menus that make organizing your military Corps more time consuming than it should be. The game over relies on scripted events to maintain historicity rather than more natural process through its own player-interactable systems.
Try playing a historically accurate isolationist USA, and marvel how little there is to do. It has some highs (the division customization, the campaigns on a strategic scale), but is anchored by LONG stretches of utter boredom, inactivity, and rigidity.

I genuinely want to regard Darkest Hour better, but it's underwhelming. Compared to other Grand Strategy games there's too much downtime, constrained decision making, and little spontaneity.