It can't be any of these things, though, if you don't know who you are writing to. Guessing who that person is just doesn't work. They can see your big fat assumptions about them from a mile away. They know that you are actually clueless about what really matters to them. So they ignore you.
If you're writing to someone you don't know, you're wasting your time. Whether writing about products you want to build or products that you have built, product managers and product marketing managers need personal knowledge of their buyer & user personas.