Earlier quoted context omitted.
I believe the subtext of that comment is that they feel it can't be "left to die" as Groups is too important in the ecosystem.
Yes, but for those purposes it doesn't matter if the email features are left to die, such as the monospace fonts that don't render or the message read/unread status that's flaky.
The internal read/unread indicator has always been janky as well. But the point is that Google depends too much on Groups internally to let it die.