There are other alternatives listed in their farewell message. Since they're no longer in service the 'notifo' field in profiles on HN and the arclanguage.org form can (should?) be removed.
Personally, I hate notifications, but of course, tastes vary, and some people really do love getting an endless stream of notifications. The trouble, or course, is which service to integrate, and how triggering should be done. It's not as simple as it might seem at first glance. Worse yet, HN (actually news.arc) runs as a single thread on a single system, so the performance impact of adding notifications might make them infeasible.