NFL is artificial and arbitrary literally by definition.
> I enjoy NFL football because it is a showcase of brain
You enjoy it because you were brought up by society to enjoy it and it was pushed on you from all sides. If you grew up in, say, Iceland, you probably wouldn't know anything about it or care at all.
> That you do not understand the game does not make it worthless.
That you clearly do not understand the history of big sports, the way they were pushed onto the public, and their explicit use in the manipulation public opinion, doesn't mean your 'understanding' of arbitrary tidbits of an arbitrary sport is any kind of argument for that sport's overall usefulness and benefit to society.
> Clearly there is some worth because football is something people pay a lot of money to enjoy
You should go look into the history of big sports and why an arbitrary artificial sport which has existed for less than 200 years is so popular in one particular country and almost entirely ignored everywhere else. Saying 'thing exists therefore it's good' is meaningless and boring.
> It inarguably creates value.
Just because something creates economic activity does not mean it's of overall benefit to society. I (and you) can very easily name many things that create(d) economic activity that we can both agree are bad for society (let me know if you can't). That doesn't change just because you like the thing, or because you know some arbitrary detail about the thing.