I did not hate it, I loved that Rumple was living his life with Belle without magic. I believe that Belle would not have wanted her life extended she would have hated him using magic to keep her young. Do I think it is completely in character with Rumple, Nope he would have secretly used magic to keep her young or slowed down her aging process or whatever, but I am glad he didn’t. It was emotional and sad but with the hope of a happily ever after in the afterlife.
I think I would have preferred them having Rumple realizing he didn’t want to live as the dark one and then having the real TLK, Belle and Gideon could be waiting off stage (where she has spent the last 4 seasons) waiting for Rumple to get back, but if this had happened OUAT could not have had their cake and eat it too. They still have not figured out how to write Rumple as the non dark one so they left him the dark one with a journey to try and get rid of it so he can die and meet Belle in the afterlife. They can still have him being shady because they can say that he is still cursed with the dark one and without Belle to keep him in line he can easily slip back into villain mode. I hope OUAT does not do this but it wouldn’t surprise me.