Regardless of whether the ending made sense or not (you can always add some head canon to make it more logical), it does not change the fact that the manga was centered around the theme of appreciating what you have while you have it.
The MC was supposed to be a parable of the regret of not expressing her true feelings and what she is willing to do to right that wrong, unfortunately, the author chose at the last chapter to:
1) Have the MC still not express her true feelings to her target by the "deadline"
2) Take away the weight of her final decision by giving her a happy ending so she has another chance to do so.
What this ultimately does is change the moral of the story from "appreciate the people around you and let them know" to "there's always another chance to tell them".
Looking at how the ratings for this manga dropped quite significantly when the last chapter is released, I would say that a fair amount of people disagreed with the change in tone, whether the ending made sense or not.