Do you find the idea of writing a newsletter compelling, or the idea of having a successful newsletter compelling?
I started my newsletter because I recognized I was constantly thinking/analyzing a specific topic, but not really doing much with that knowledge, and could not find an existing community focused on that topic. I started writing to put into words what I was thinking, and found I really enjoyed writing with an audience in mind, even though I had none.
If someone signs up for a newsletter of yours, that is pitched as some sort of original writing, there's a very high chance they're going to read it. If they stop reading, or unsubscribe, you can ask them why, and get valuable feedback so you can improve your writing. You end up with someone interested, or feedback. I see it as a win win.
The bigger problem is finding the hypothetical audience!