There are many shows I have watched that have been cancelled on a cliffhanger that I still enjoy thoroughly.. but some shows can get ruined by an inadequate ending or even an inadequate direction.. For instance, look at Pretty Little Liars. We could also talk about how the perfectionists was cancelled after a season, but I digress.. But other shows like Shadowhunters or Witches of East End can be rewatched endlessly even though they were cancelled on a cliffhanger. It all depends.
Was there an earlier period for which the show could have ended where I could use as a line of demarcation? For instance, one could watch the first five seasons of Buffy and choose that that is their preferred ending as Joss had thought that they wouldn't get renewed after season 5...
There are anime for which I feel that I cannot continue to watch if one of the main characters becomes excessively cringe worthy.. Like a female character who remains hopelessly obsessed with another character who has proven to be the scum of the earth... lol. But for cancelled series; series that I used to like, but I have since hated the direction of the series I will often read a fanfiction given that someone has written one.. And trust me.. There are plenty of people who have written a fanfiction that in length is the equivalent to a 800+ page book. lol