I would say it depends heavily on the game. On the other hand we got games with "do this 20 times, there isn't any variation on the images / actions" and then there is games where you feel like you are progressing.
The grinding without any meaning is like bad sandbox without any content: click around and waste your time.
It depends. Grinding may be boring, but a system of effort and reward are necessary in order to make a game work. The player needs to work, and the author needs to make it worthwhile.
(1) "Such a Sharp Pain" and "Neet and Angel" have great visuals but you don't really work much for it -- they're easy
(2) "Haley Story" and "Man of the House" has a lot of work, to the point that the reward isn't enough -- they're grindy
(3) "Long Live the Princess" and "Bones Tales" has the right amount of effort and rewards.
Not to take away from any of them, as all of these are great games imo.
It's important to telegraph progression in advance. In the original Big Brother, I used to click through the repeated scenes really quickly and I'd often miss the new content the first time. With no rollback, that was pretty galling for events that only happen once a week, say.
Not a fan of this type of grinding at all. I really feel that some amount of grind enhances the story, but only if it is done well. I think certain combat grind systems work really well. For instance in Mist. It heightens the experience and gives a sense of urgency and accomplishment. As apposed to one that doesn't work like in Rewind. It becomes so laborious and lengthy that I forget that I'm playing a porn game.
There is a VERY fine point between acceptable grind and slog, the vast majority of games fail to find it, especially since it is a somewhat personal thing as well.