Again, he feels guilt for them risking his life just to save to save him. He says i lived the best i could and i hope that was enough for what you guys did for me. Thats the whole point of Miller's earn this speech, and how ryan feels later on in life. And sacrifice for the next guy is the whole point of war and the military.
Apocalyspe Now cant be compared. It's not a real representation of war, and even then Sheen kills Brando. So his mission was successful too.
"live the best that he could" doesn't sound like guilt to me. Again, it is paying homage by living the best long life he possibly could have because those guys paid their lives so he could live his. That's not guilt.
And again, this is about Spielberg's typical standard in mostly concluding his films on a positive note. With the exception of Munich, all of his films are wrapped up neatly in a uplifting note of some kind of closure that can inspire. And reality is not like that. Apocalypse Now is an example of the total opposite. It showed or exposed war in its true light.
Dunkirk, and I just watched it again last night, basically manipulate perception versus reality. Everything in this intertwining timelines exposed a perception that contradicts the reality and it is summed up with Churchill's speech talking hella shyt like "yea, y'all had up against the wall, but we're still here", when the truth was that the Army and Navy were very unsure and scared of what they felt was a certain demise.