But that is not good enough, it only covers the case of new customers.
I, for example, installed some of those managed applications, some years ago, to try them out, decided they all looked horrible, and simply walked away.
Should I have deleted them?
I don't know. Arguably yes, arguably no.
(Of course, now I've deleted them all. But that's only because I read this forum.)
Did Dreamhost send me notification that they were stopping maintaining those apps?
I don't think so. Maybe they did and it went into my spam folder (which in itself is a major problem that the industry is not properly addressing, in my opinion).
I suspect that they never sent notification.