To get a few things out of the way:
As such, I don't really know much about the current format and degree of information, however imho, a newsletter should do what the name implies: It should contain news. New things. I would be interested in a quote, a Hashnode changelog, WIP features and hot topics and highly upvoted/appreciated posts which I did not view, yet. All in the context of my followed communities.
I very much enjoy the weekly Rust update. It's not called a "newsletter", because it contains so much more. It's called "This Week in Rust." It starts out with a small description of what Rust is and wants to be, so that everyone is reminded regularly and there are no doubts about the goals. Then, they list the most important stuff: Articles and blog posts; 10 in total. They have a crate of the week (post of the week for Hashnode?), call for participation (which questions need attention on Hashnode?), updates from Rust Core (Hashnode changelog and WIP?) and at the bottom events (Hashnode does want to sponsor events, right?), jobs (new Hashnode jobs) and a quote of the week (there you go, a quote :D).
This is just my opinion, and I really don't want the Hashnode newsletter to just copy this format. So far, I really appreciate the weekly Rust letter content and I think many websites could learn from it.