We did not try to get Kane. Because ETH did not want Kane. It is that simple.
Last year, we tried to get De Jong for months. De Jong quite clearly told us that he did not want to join us, but we still tried, we came into agreement with Barca, and we waited for the player to change his mind. With Kane, we did absolutely nothing. Kane did not reject us - because there was nothing to reject. ETH did not want him, we didn't try, end of the story.
If you think Kane would have been good for us then question ETH, if you think Kane would fail with us then give credit to ETH. It was his decision. (As it was his decision to reject De Gea, the club wanted to sign De Gea. ETH makes the final decision for all transfers, good or bad. )