IMHO... there are few occasions when spoilers truly ruin a film. "The 6th Sense" as one. But that's very, very, very rare.
But 99 out of 100 times? A "spoiler" doesn't ruin anything unless the individual wishes it to.
IE, those who want spoilers should be free to have them and those who do not, free to avoid them.
Depriving those who want them from having them simply because the person(s) with such knowledge thinks it's best, IE are 'protecting' people from themselves and their desire for such knowledge... that's nonsense and a bit arrogant of anyone thinks along such lines.
If you know how a film plays our or ends, and people want to know, you should tell them without hesitation. It is their decision whether they wish to know.
To hold back out of a sense of "oh, I'm saving you from ruining it for yourself" is patronizing.
People are different. Some people enjoy knowing and seeing it play out. Some people don't like surprises. Why is that so wrong? Why is it so hard for people to grasp? Why, because the majority do enjoy such, do the minority who don't have to suffer at the whims of those with such knowledge who deem themselves suitable to make decisions on others behalf?
Tell those who want to know. Do not tell those who do not want to know.
It's pretty simple and easy. And people who hold back information to try and "help" people who want to know from spoiling it for themselves? ... Get over yourself. Seriously.