The NBA is the best basketball league in the world. So for any player to ever reach the NBA and play in the league is a massive accomplishment, as it means that they are some of the best players in the world. But it's the players that are truly elite that end up becoming superstars in the league.
Some players enter the league and almost instantly become superstars. Players like LeBron James, Michael Jordan, Magic Johnson, and many others instantly dominated the league when they first joined the NBA. But some other players usually take time to develop into superstars.
Each player in the NBA develops at their own pace. Stephen Curry is often considered the greatest shooter in NBA history. But his first few years in the league were not an indicator of that, as Curry only became an All-Star when he was 25 years old, within 4 years of being in the league. And from there, he went on to cement himself as one of the greatest players of all time.
This was also the case for Steve Nash and Kyle Lowry. Both players are now considered elite point guards, but it took them a long time to reach All-Star status. Steve Nash was 27 when he became an All-Star for the first time, and eventually, he won 2 MVP titles. Whereas Kyle Lowry didn't become an All-Star till he was 29, and he went on to win an NBA championship late in his career.
Whereas someone like Kawhi Leonard, who is considered one of the best players in the NBA today, did not even average 20+ points per game until his 5th season in the NBA, even after he won an NBA championship and Finals MVP. Leonard would do the same just a few seasons later.
Jimmy Butler, one of the best players in the NBA today, was not considered a top prospect. In fact, before he entered the NBA, he spent a year at junior college before he eventually got to Marquette and became a first-round pick in 2011 when he entered the NBA.
So clearly, players develop at their own pace. If players were expected to become superstars immediately after entering the league, these superstars would have been discarded by their teams and the league pretty soon. And we should have this same patience with some of the current young players in the league.