In this scene from Harry Potter and the Deathly Hallows Part 1 (2010), powerful Dementors are unable to break through an elevator door:
Why couldn't they break through it?
In this scene from Harry Potter and the Deathly Hallows Part 1 (2010), powerful Dementors are unable to break through an elevator door:
Why couldn't they break through it?
This is evidenced by the Dementor on the Hogwarts Express (Prisoner of Azkaban), who had to open a door to enter the carriage.
(1:36 to 2:02 in the above video)
We can expect that the Ministry doors are more heavily enchanted doors than the ones in the Hogwarts Express (a government building vs a school train- seems kinda obvious). So the "hand-waving to open door" probably wouldn't work on them.
And of course, it's for dramatic effect (a "close shave" moment).