Mark 16:8 : They went out, they fled from the tomb, for trembling and astonishment had come on them. They said nothing to anyone; for they were afraid.
An immediate objection to the hypothesis that GMark should end at verse 16:8 is aesthetic. The ending is "abrupt."
Aesthetics weighs little in guildly deliberation compared with the fruits of text criticism which assure us that 200 or more years after the gospel was composed, verse 16:8 appears in all the complete ancient manuscripts, while the witnesses disagree among themselves about what, if anything, may have followed 16:8. Text criticism is also the discipline where all bugs can be spun as features: the very fact that 16:8 is so unappealing as an ending supposedly reinforces the conclusion that it is the proper ending.
Another perspective on the question is to reason from anology.
Like Mark's gospel, the 2004 Oliver Stone film Alexander is framed by a narrator. In the film, he's dictating his memoirs to a scribe. (* Spoiler Alert *) Toward the end, the narrator confesses to his part in a plot by Alexander the Great's generals to murder him. The betrayed hero dies. That's the end of the main story. The narrator directs that his memoirs be placed in the Library of Alexandria. That's the end of the narrator's framing story.
But there is one more thing revealed: an "end card" that says that those memoirs vanished along with so much else in the ill-fated library.

Wait - if the memoirs vanished, then how could Oliver Stone know what was in them?
Wait - if the women never told anybody, then how can Mark know what they would have said?
It's a bit more complicated than that in both cases, but the net effect, IMO, is much the same. Alexander openly admits (or reminds us) that it isn't strictly historical. If Mark ended with the women's silence, its "end card," then it too openly admits (or ...?) that it isn't strictly historical.
That explicit divorce of the story world from the real world is a different problem from aesthetics and the problem of tardy textual witnesses. If you fancy reading more about it, more is here:
https://uncertaintist.wordpress.com/202 ... pt-ending/