The episode was just simply uncalled for. Something like this might have worked as a forgivable almost half-decent filler somewhere around mid-season. At least that would have payed off, because then we could have had the wedding episode as an actual fitting season finale.
This episode was exceptionally poorly written, the actors did a surprisingly bad job portraying their characters' past selves and, except for Grace's big announcement in the very last second, NOTHING ACTUALLY HAPPENED THROUGHOUT THE ENTIRE FINALE!
I'm confused about the writers' decisions and I'm very disappointed.