Just as the title says, I recommend you ignore the low ratings. This is because I truly believe those who have rated this drama as under 7 have either a) never watched a Japanese drama or b) truly did not understand the story.
Without containing any spoilers, I will try to summarize what I believe to be the primary motives, or rather the point of the whole story. Please keep in mind that I'm also accounting for Season 2, which doesn't seem to be recognized in the actor credits here.
Jin (or Time Slip Dr. Jin in the manga) is the primary protagonist of this story but he, like every good protagonist is fundamentally flawed. He can't forgive himself for his mistakes and it plagues him throughout the story; whether it be with reference to Miki, or any other patient he attends to, this uncharacteristically good nature of his inevitably disables him as a person, especially a relatable person.
For those who have felt as if they haven't made a difference in the world, or what you do is not enough for others, HE is your character foil. But the story isn't about how flawed he is, it's about understanding one's limitations, and accepting the fate that has been handed to you -- in essence, accepting that you, like any other human on this planet, has their limits. Does that mean that fate is inescapable? Not necessarily, it simply means that we sometimes have to realize that whatever paths have been laid out for us, fate, or destiny is drawn out by those who surround us just as much as it is effected by us.
Ultimately, this story does raise questions (perhaps religious ones), but allows us as the viewers to draw conclusions for ourselves. If that isn't your "cup of tea" then I suggest you watch something less thought provoking... like a Twilight movie.. maybe that'll be better suited towards your tastes.
