When I was younger, I wasn't the greatest at math. My parents quickly realized this and signed me up for a math tutor in the summer time. My parents had the expectation that the tutor would correct my order of operations, my understanding of multiplication tables, and logic problems so that I my process and my answer would be correct. Thankfully it worked (for a little while).
However, if my parents would have sent me the tutor and the tutor had not adjusted, changed, turned my thinking around, and instead said something to the effect of, "We aren't trying to change anything he's doing. He's still muddling around in the numbers and getting wrong answers. But as a tutor I just want him to be him and enjoy his time," - that tutor would not have a job for long.
When we come to Matthew 4:17, a similar idea emerges. The text says,
"From that time on Jesus began to preach, 'Repent, for the kingdom of heaven has come near.'"
It would be a little anti-climactic if the people that were "sitting in darkness," "dwelling in the land of shadow and death," and stuck in their sins encountered "the great light," "the dawning light" and the light said, "Yea - I don't really have anything better for you, I'm not gonna give you an alternative way to live, I'm here but you're going to remain stuck" - there wouldn't be any good news to the light except to expose that we were stuck, but the misery would remain.
The good news of the Epiphany season is that when Jesus manifests himself, shows himself forth, he offers a way out, a better way to live, freedom from the stuck.
That's what "repent" means - to change, to turn around, to go in a different direction.
Repentance means we don't have to stay stuck.