That is the context of His earthly ministry. It's just that simple.
That was not what Jesus was talking about in that passage.
How's this for "wanting to bring gentiles into the picture of His redemption"?
Matt 15:21-28 (AKJV/PCE)
(15:21) ¶ Then Jesus went thence, and departed into the coasts of Tyre and Sidon. (15:22) And, behold, a woman of Canaan came out of the same coasts, and cried unto him, saying, Have mercy on me, O Lord, [thou] Son of David; my daughter is grievously vexed with a devil. (15:23) But he answered her not a word. And his disciples came and besought him, saying, Send her away; for she crieth after us. (15:24) But he answered and said, I am not sent but unto the lost sheep of the house of Israel. (15:25) Then came she and worshipped him, saying, Lord, help me. (15:26) But he answered and said, It is not meet to take the children's bread, and to cast [it] to dogs. (15:27) And she said, Truth, Lord: yet the dogs eat of the crumbs which fall from their masters' table. (15:28) Then Jesus answered and said unto her, O woman, great [is] thy faith: be it unto thee even as thou wilt. And her daughter was made whole from that very hour.
It was not until she humbled herself (as a gentiles) and elevated Israel that Jesus would even talk to her.
Jesus died for the sins of the whole world. But that was not made know during His earthly ministry. That was why He called Paul, years later.