Devils advocate from a out of spectrum writer who thinks the very concept of a main character is over depended on: don't readers assume the MC is going to have plot armor and be safe somehow anyway, because it is in the writer's best interest to keep the MC alive and continue the story. Plus...
Nor should it kill the suspense. It feels like a hollow assesement This can be argued with any story where the main character has plot armor. The reader is not wondering 'if' the mc will overcome the situation, but how.
Oh, btw, I don't think such a structure merits any demotion in quality perception whatsoever. It can be done really well. I just don't like it as much as a fresh start story.
I tend to block out anything that makes a narrative less interesting to me. If you tell me the end, my brain erases it automagically. Unless it's really vague, I didn't mind the little statement at the start of Boku no Hero.
But both are so freaking long I tended to forget they were intended as foregone conclusion. And I didn't trust the the gods in the Odyssey. ANd Boku no Hero kept the outcome rather vague of what exactly becoming the greatest hero would specifically look like.