A loud amen! I barely have time to read anything else since I started on Medium, let alone newsletters from authors trying to entice me to buy their latest books. As you say, the ones I care most about I follow on Twitter. It’s hard enough to keep up with that stack of TBR books on my bookcase. I would rather read those books than newsletters tempting me to buy more.
As for writing a newsletter, everyone says it’s the best way to hang onto readers so they don’t miss any of your work. I’m not doing it. It’s one more thing to write and I’m not trying to be a brand. I’m a person. I hope if people read my posts here or on my blogs it’s because they learn something from them or enjoy them. All my blogs have a way one can follow them if one wants to. As for newsletters, I’ve got a lot to unsubscribe from.