[Serious] Generally speaking, is philosophy a worthwhile subject of study?

[brewer]

Yes, I think food for the mind is important, but that food is found in many ways that do not need to be based in philosophy. Can a mechanic improve his skills with learning more and better techniques? Can someone learning to sew expand their mind and creativity? Or the first farmers testing how to improve production? Questions and resultant answers or acquisition of skills (mind food) do not need to be derived only from philosophy.

Yes. Those things qualify as "food for the mind." 

So does art, literature, poetry, and (sometimes) network TV. I've been watching Star Trek Discovery. How practical is a science fiction show about aliens and space fantasy exploration?

Let's say we remove a couple "impractical" things from humanity's buffet of food for the mind. Let's take away art and poetry. Is humankind better off? I'd say no. I would say they are worse off. Art and poetry enhance humankind by bestowing catharsis and sometimes creative power to those who appreciate them. It's hard to quantify what practical use art or poetry has, but it could be argued that such things are --indirectly-- of practical use. I would argue that philosophy is one of those things (like art and poetry) that enhance the human experience. Is philosophy all-important? No. But take it away from humankind, and we will have lost something immensely valuable.

***

I could also argue that philosophy IS of great practical import. In America we have inalienable human rights. The concept of inalienable human rights didn't come out of thin air. Nor did it come from someone trying to found a great nation which protected its citizens liberty via the concept. 

It came from a thinker who asked the question: What is justice? 

Inalienable human rights played a crucial role in his answer to that question. He then formulated a set of logical arguments bolstering his position. An intelligent person (Thomas Jefferson) found those arguments convincing and applied those principles to his work in nation building.

The reason Jefferson was convinced is because John Locke made a convincing case that relied on few assumptions. That's what philosophers do. And that can be of immense practical value sometimes.

I don't believe I said art and poetry were impractical, but would say a fare share is not my thing. I was a musician (mainly piano/sax) and vocalist thru high school. When has entertainment been ever considered impractical?

What makes you think that justice and human rights is only derived only from philosophy? I don't think early tribes spent to much time developing a logical argument for 'killing within tribe not good'. Yes philosophy added to reason but not necessarily action.