While it's true that any subject can be made more interesting by a proper choice of composition and lighting, you should still try to find compelling subjects for your portraits, landscapes and other genres of photography.
Don't settle for mediocrity – photograph people that you find most puzzling, explore the weirdest streets in your city, find the most beautiful flowers or insects if you're into macro photography. You'll notice that really interesting subjects will make you more engaged – it's hard to put efforts into shooting something that doesn't make you tick.
In fact, in Adam Williams course on how to win photo competitions, he specifically singles out having a single main point of interest as one of the keys to doing well.
Engage In Storytelling
Have you ever tried to tell a story with a series of photographs? Storytelling might sound like an annoying task you don't want to think about, but in fact it can make your photo shoots much more powerful both aesthetically and intellectually.
No matter who or what is your subject, take some time to ponder over it. Ask your self the following questions:
What can I do to capture different facets of my subject?
Will changing a perspective or lighting reveal something new about my subject?
Should I introduce a couple of props that will help viewers understand better who my subject is?
What emotions do I want to convey?
Have I established a meaningful relationship between the main subject and the background?
Answering these questions will help you organize your shoot and avoid repetitiveness in your images.