I would think V'ger annihilating three Klingon warships would be enough for that rather than also including the destruction of a seemingly unarmed space station especially since the Klingon battle actually gave an impression of how unstoppable V'ger seemed whereas all you get from Epsilon 9 is that it's capable of destroying a defenseless com station(?).
I don't see that logic. The Klingon incident was a replay of a past event. Showing a second "attack" helped drive home that this was an ongoing, approaching threat. The first attack was against an alien power, an enemy; but the second was against fellow Starfleet personnel in a Federation facility. It struck closer to home, both literally and figuratively. The emotional impact of that should be self-evident. Think about how much more strongly Americans were affected by Pearl Harbor than by the invasion of Poland.
Escalation is important to drama. In the first and second acts of a story, you need to show not only that a threat exists, but that it's ongoing and intensifying. If there had been no illustrations of V'Ger's threat between the Klingon incident and the
Enterprise's encounter, the stakes wouldn't have felt as high. Moreover, it was necessary to show two separate attacks in order to demonstrate that the Intruder wasn't just targeting Klingons, but was targeting
anyone that got in its way, Starfleet included. Without that, it wouldn't have been as clear that the
Enterprise was heading into danger, and that Earth itself was under threat.
So yes, the Epsilon 9 attack was absolutely essential to the story.
I think the destruction of San Fransisco was less about "disaster porn" than it was about the attack on 9/11...
But that's just the problem -- lately, the two seem to have become interchangeable. Movies are playing on 9/11 imagery, but not to make a statement, simply to indulge in spectacle. 9/11 wasn't just about buildings falling down, it was about the human cost, the shocking emotional impact. And that's what was all but missing from STID aside from a token acknowledgment at the end, and that's what was completely and utterly missing from
Man of Steel. And so if those were attempts to comment on 9/11 in some way, they failed profoundly. By contrast, the Marvel Cinematic Universe got it right -- the human impact of the attack was acknowledged during the climax of
The Avengers, and the aftermath has been addressed in two subseuqent installments of the franchise,
Iron Man 3 and
Agents of S.H.I.E.L.D. It's more than just empty spectacle there.
(Note that I do expect the makers of the MoS sequel to include some belated acknowledgment of the human cost. But since it was so cavalierly ignored in the film itself, I don't think that will entirely redeem it. At least in the MCU it all feels like it's of a piece, like it was planned that way all along rather than being an afterthought or patch job.)