Only book smart, he's still the human equivalent of osmium
Well... I can't blame him for that.
Kuromiya clearly said (even if he doesn't know) that her only intention is that he fall in love with her (which he is already has, thus she is also dense), but that she doesn't want to go beyond that. We all know this is BS and that she will not be able to keep things platonic.
In other hand, he knows she is an idol and that if he made a move, there would be two outcomes:
1) He is rejected
2) He is not rejected, but now her career would be at risk (godhowIhateidolcultureandthatpartwhereidolsaretreatlikeaproductmadetocreepparasocialdudessomeofthenbeingmiddleagedman why god? Why does this need to exist?)
Thus, he knows he can't focus on romance, not with her. Part of him may be denying any possibility of Kuromya liking him because of the closed path in their futures (and also, he has low self-esteem)