Because it was a true assessment of his performance for the 1st innings when he dropped at least 2 vital catches. but if you wish to think that his performance in the field was acceptable that is your prerogative but it doesnt mean that I have to agree.
Its the ones he dropped that are the cause for concern. he is put in the slips because he can catch them so if he drops a couple that is a disaster as he isnt doing the job he was put there to do. That is apart from his batting.
IMHO he is a poor captain and the captaincy has affected his batting but perhaps he will learn and get better. The other point is who is there that would do better?