PointAndFail

All I can add to what many people have already said is that you might want to look into Overlord and The Eminence in Shadow. Two animes that show what you can do when you have an overpowered protagonist. (Ok if you dont want to look into them I can give you my take. Have interesting side characters and give them good development. And then just make sure to make fights cool when the MC fights and inevitably wins. Overlord, One Punch Man and The Eminence in Shadows all generally do something along these lines and they are well received. Well it is a lot more nuanced than this but I think most people will be happy with just this)

The pacing is exceptional. Most of the time, sports novels (or fanfics) drag on and on, being very repetitive. It's good that you were unafraid of summarising a lot of matches as they eventually become, "How many different ways can you score/ Someone does something in a match" for a few hundred chapters. There were points in the story where I was confused what was going on (I think it was probably the English) but I could not stop reading. All the free time I had was spent reading until I had reached the final chapter. It really feels like the whole story was planned from beginning to end, which in most cases, makes for a compelling story. You knew the kind of story you wanted to tell and the content for each volume. I kind of wished more stories were like this and less wish fufilment and more realistic. If I had to say what I felt is missing from this story, I really want to know what the Main Character is doing after he retired. What are his children doing? What about the sports clubs he invested in? I cannot help but want to find out what happened there. Anyways, great work! If you do write another story, I will be sure to pick it up.