I don't disagree with you generally, as I stated I was a fan of both MoS and BvS, but despite the montage, he still has done that much relative to the character when he dies in the comic. No one is saying that he wasn't a hero and that his death wasn't tragic, especially from the DCEU world's perspective.
Superman died after 60 years and hundreds of issues in the comics, while in the DCEU he died in his second movie - to me, this is why it lacks emotional resonance with the audience, unlike when Iron Man died in Endgame, he had been around for 15 years in the MCU world, 11 in ours and in nine movies. A montage isn't comparable to nine movies worth of heroics and character arcs.