I don’t know how this can be possible not to be aware of landing even without announcement.
Personally I always feel the change in sound and speed the moment we leave the cruising altitude. Few minutes later the top of decent is announced and landing in 20-30 minutes. As the minutes pass, the flight usually gets bumpier, there are more turns than before, and when the landing gear is out, everybody can hear it and feel it.
So if I notice all that how can a flight attendant who flies much, much more than me be so unfamiliar with normal flight procedures and just wait for the big announcment from the flight deck?
I know they might be busy, but don’t they plan carefully all the work according to flight time and service requirements specific to airline and class? So I guess they must be aware of time and landing can not be such an unexpect event even without announcement