With the exception of Game of Thrones and Westworld all their new content is terrible. Even the bad Netflix originals like "The OA" are better than the garbage on HBO. And that's actually the problem with the Netflix business model. It's become just another HBO. And the problem with that is once you become just a content studio you're entire business model is a slave to your talent. Once the people currently in charge of content production get too old, leave or lose their current edge in some other way the business will start to come undone a la HBO which certainly has seen much better days. I love Netflix but wouldn't own the stock.
The thing about HBO is people will pay the subscription fee every month for just one of those shows. One really good show with very high production value like Game of Thrones, Westworld, The Sopranos, and even short stuff like Band of Brothers or The Pacific, and you can milk that show and move on to the next. I'm sad to say I am one of those people. I hardly ever watch HBO currently outside of Game of Thrones, Westworld, and a movie or 2 on demand. BUt those shows are good enough for me to justify keeping my subscription up. GoT is winding down but Westworld should have some decent legs, especially if they can expand into the world (and other parks) outside of the Westworld park itself. They just have to keep finding that one show(hell, just make sure to cast Ed Harris in a major role and I'll probably watch it, he makes one hell of an ambiguous bad guy).
If there is any real threat from Amazon/Netflix/etc it's not necessarily the quality of the show that will do in HBO (of course they do have the quality with shows like OITNB, Stranger Things, and Narcos) but more the fact that, for so long, HBO was the only place where you could find shows like that, that they could have content that other networks couldn't. But now you can find that content on Netflix or Amazon. That's the real danger.