I don't feel the same, seeing the early stages of Kenta's journey has been a joy to me.
He is one of the deuteragonists of this story, to me, Kiyo, Sumire, and Kenta are equally important to this story... this would have survived for far less time if we stayed only with Kiyo, she is the "rock" of this story, always there, always stable... but she doesn't really change, she just "refined" who she already is, but she is the pillar that allows everyone to become better.
Sumire is the one advancing things, she is the one with ambition, wanting to become better in her craft, but at the same time needing to balance that ambition so that she doesn't burn herself out.
Kenta is the foil to Sumire, he has the same level of ambition as her, I would argue even the same level of talent, but his is more "subdued", it depends on him making a hard-fought decision and working hard, than Sumire's almost superhuman abilities, but he achieves what he sets to do.
This story is a "juggle" between these three, and others too, varying who we stay with, advancing their little stories, and then showing the result in the story of another.
So... I think it is appropriate this is ending with Kenta, because after we see this early moment of his coming to Kyoto, we will see how it connects to the rest.
And I have the inkling this will have an "open end", something like... we saw the starts of their journeys, how they already inspired each other and others, but it is still early in their lives, maybe Koyama-sensei gives a glimpse into their futures, or maybe she just... leaves it to the imagination, this series ends, but their journeys are still going in the minds of those that read this story.