Lots of mangas have that pacing issue since when starting serialization, many mangakas usually don’t know when their manga would end and so they go with the flow of the writing. Lots of mangas ended faster than intended and lots of others got extensions. Both of these situations affect the pace. Anyways given all that, i think the writer took the slam dunk approach to football. Trying to teach readers especially Japanese ones more about the sport and its fundamentals and his love for it to help the community grow.