This seems somewhat absurd at a glance, but hear me out.
Changing the way the game is played is a certain kind of influence, but I am not considering influence more broadly. Certainly MJ had a vastly larger influence on basketball culture. Larry Bird and Magic Johnson brought in more viewers, and of course everyone yells "Kobe" when they shoot a balled up piece of paper into the garbage. All of those players might be more influential on a broader level, but none measure up to Dirk in how he changed the way the game is played.
A little background to illustrate the point: I was tall at a young age. 6'2 in 7th grade. I was not an uncoordinated, gangly tall kid though. I could dribble, I was fast, I could shoot threes, my one dribble pull up jump shot was my best move. I still dominate lunch games with it. Despite it being highly efficient, none of my coaches let me play that way. They saw a 6'2 middle schooler so they plopped me down on the block and had me post up. One time a coach I didn't play for told me he would bench me if I shot a three during a game.
This was the way people thought about basketball at the time. Several years later in HS, I hit 2 threes in a row and was taken out for taking bad shots. This is true despite only growing 1 more inch. But at a small high school, I was still one of the taller players on the team and supposed to be on the block. They only reluctantly let me play my mid range game.
This is not even remotely true anymore. The way the center position is played today is hardly recognizable from the 90s or even 00s. People will even make the argument that Shaq wouldn't be as successful in the league today because it is such a different position. Embid, Jokic, Towns, to name only a few, can all shoot threes. This transformation is due to Dirk Nowitzki demonstrating the value of big guys stretching the court. And not just as a role player like Rasheed Wallace (though Rasheed didn't really start shooting threes until people realized how exceptional Dirk was) or Okur, but as the franchise player.
The figure below shows how centers have changed the way they play. There is an enormous increase in threes attempted per games beginning around 2012-2013. This makes sense as it took a while for the next generation of centers to enter the league and dirk didn't get his ring until 2011. Guys like KG or Duncan weren't going to become three point shooters. As the next wave began to enter the league, it is apparent they were trained to play a different way than previous generations.
To illustrate this point even further, Zach Edey, a two-time national player of the year (I think) center is projected to be a late first round or early second round draft pick. If he played in the 70s- early 2000s, he would have most likely been a lottery pick if not first overall pick. The reason is because his game won't translate to the NBA. This is important because not only does not being able to play outside make you less valuable, but entire offensive systems are predicated on their bigs being able to shoot outside.
This is in opposition to Wemby. If he played in the 70s - early 2000s, he would have been plopped down on the block and been a slightly better Shawn Bradley.
To me, this means Dirk has changed the way the game is played more than anyone else. The entire philosophy around the role of big guys has changed. Offensive systems require that their bigs can shoot from outside. No one else has had this amount of impact on the way basketball is played.