There is an unlimited amount of ideas and topics to write about. Writing can be enjoyable. Enjoyment and elation are good emotions to experience! One can write fiction or non-fiction. Fiction writing can take on many forms. Long novels and short stories can be be published in the realm of fiction.
Every concept that exists can be written about. There are an infinite amount of different topics to write about. That is a pretty exciting idea to think about, it seems, perhaps. Humans can become professional writers. Humans can be paid to write. Just about everyone needs to earn a living in order to provide for basic needs like food, water, and shelter.
Reading what others have written can be useful. One can learn from reading. Reading can stimulate new ideas. Then, one can write about those new ideas. It can be like a positive feedback loop, or cycle.
Writing for others can be useful. Sharing knowledge can be useful. There are many types of knowledge to share. There will likely always be more new knowledge to discover. Research is happening all the time.
More humans should take up writing. This could help the economies of this Earth, perhaps, both directly, and indirectly. Additionally, more humans should read more. Education is good, and through reading, humans can become more educated.
One can use a pen to write, a pencil, a keyboard, or even a cellphone possibly! It is perhaps useful to keep some method of recording ideas around at all times, so no good ideas will have to go to waste. And it should perhaps be noted that there are many good ideas, but ultimately it is those who impliment the good ideas that often are rewarded the most.
So, there are many topics to write about, perhaps an unlimited amount of topics. Writing can be enjoyable and useful. Be creative and curious in order to discover new topics to be able to spend time writing about and sharing with others.