Easily haki... Look at the top of the one piece world, 4 have no fruit powers.
Although you can be bad at the haki you possess, you can also be bad at the fruit you possess, so this cancels out. I'm just assuming you'd become expert on what you have.
Also, even for those top of the world fighter characters like the admirals, Kaido, Big Mom, WB, Sengoku etc, I think most of their combat power come from their own skills, just utilizing fruit power to enhance/compromise with it.
Finally, if in the real world, haki would get me a long way under all circumstances. Fruit powers would just make me look like a freak and be targeted by authorities 24/7.