These sports in general provide value in the sense that many people find them worth paying for. That's the definition of value.
Now, it's true that they're not generally excited to see the #503rd ranked player in the world play the #489th ranked player. But, the top 50 players in the world were once ranked at the bottom. They played their way up.
In other words, how would you know who are the best players in the world unless you have a large pool of professional players?
Like many, I have a lot of issues with the way tennis rankings are calculated and the way prize money is distributed. You need those lower ranked players and therefore they should be paid more.
But make no mistake D1 and Pro-Circuit players are, at the end of the day, still very good.
That is improving at something that is completely useless still. It is not even more interesting to watch than, say, 20 years ago. That progress does not help anyone.
It is not the same with sport. You being 0.05s faster swimmer does not make swimming competition more fun to watch. Same with skiing or whatever. And pretty often, the performance improvements make the sport more boring to watch due to predictable optimal tactic.