idk what people are talking about. it's slow bc if Konshikawa had feelings for a girl like 15 years younger than him, especially his subordinate, it would be improper conduct and not in-line with his characterization.
the fact is that misato must make the first move or else the power dynamics are really unbalanced.
ofc her efforts can't change his feelings that fast, or it would be unrealistic. she also can't be too aggressive, as it's not in-line with her characterization either.
the new guy isn't a creep, misato isn't taken and he hasn't been rejected so he's free to try and get closer to her.
this isn't a high school romcom, in fact a gradual development is probably the only way to tastefully execute this concept.