If I want to be "engaged" by some form of media, I keep the tab open until I consume it. Either that or it ends up in Pocket, where I might happen upon it on the next visit to getpocket.com/random.
Newsletters slamming into my inbox means it's just going to get lost in the noise -- context-switching notwithstanding (though probably the biggest factor), I can't imagine being so unimaginative that my curated media intake consists solely of ~5 sources who are trying to shove their often clicks-driven (thus intellectually compromised) content into my awareness.
There's an argument that newsletters are for those creators whom you just can't get enough of, and the other more serendipitous/algo-driven content in your feeds can be a more diffused supplement to the core offerings. And sure it just comes down to who prefers what. But contending with the constant onslaught of newsletter banners/modals/whatever pushes me to throw the baby out with the bathwater. There's enough creators out there that don't do that that it's actually a premium when I'm not constantly assailed by nudges, etc.
Like you, what I don't understand is the email sign-up form popup companies push in front of you on every visit. Nobody wants your "newsletter". Nobody wants to be signed up to your newsletter when they sign up to your service or buy something from your store.
