Actually Sakuragi grows as a character and changes quite a bit throughout, even though he's still a cocky kid.
I didn't mean exactly Sakuragi, but everyone around him. While he does change, Inoue kept introducing new characters, mostly from the other teams, and showing us flashbacks of them, while still trying to further develop the Shohoku characters in the middle of the games. In my opinion, because of having to deal with so many new characters, it was impossible for him to focus so much on Shohoku like I hoped he would.
Unless you mean they continue to have to win basketball games, I think you're mistaken. There's plenty of character development, which to me is the backbone of the series.
I guess I did exaggerate when I said everything stays the same, especially because Sakuragi not only learns how to play, but he learns how to control himself and use his head when he got the ball: all these actions which reflected on how he started to act out of the court as well... and it was all done quite well. But I don't know, I still feel like Inoue could have developed his relation with Haruko, or show more about his past and what happened to his father. Some things just felt like Inoue forgot about them or didn't care enough to mention it again. And that's just Sakuragi we're talking about, my problem is mainly with the rest of the team.
Mitsui goes through the same problem for the last two or three games:
he got tired to the point of passing out because he stopped his training; Miyagi
loved Ayako and did his best when she cheered for him... and while all this was awesome, I expected something else would happen to them. I mean, aside from the things I mentioned about these two characters, we only know that they don't like to study and were troublemakers. To be honest, now that I'm talking about it, I admit that I sound bitter, but I'm not saying these things out of hate to the series. I guess I just expected more about the characters because I like them a lot, or maybe I got that impression for reading the whole thing in such a small period of time (like, two months).
Again, if by "exactly the same" you mean they play basketball during all the major events, then... yeah.
The games themselves felt similar in many parts because of what I mentioned earlier: the main characters (excluding Sakuragi) had the same problems to deal with at the first games and at the game with Sannoh.
Part of Slam Dunk's strength is that it's an ensemble effort, not just one guy's journey.
That's just it, although it is an ensemble effort, to me it felt like the only character that gets
really developed is Sakuragi. For example, Rukawa existed only as his rival in the series, we're not shown almost anything about him. We know his ambitions, but that's only introduced halfway through the series.