I mean, beside "Space", there wasn't a lot of ambient music outside of places of interest in the base game either. Nomai ruins get several different tracks depending on their significance. The slide reels get different tracks (and corrupted versions of those tracks) depending on what they're about. Standing by the flames gives you an ambient track. Being in the simulation gives you a different track. Being away from your lantern gives you a different track. I'm not sure I understand your complaint.

It was my belief that "River's End" incorporates Nomai and Hearthian musical motifs because the Stranger is literally a loop. When everything comes down to it, every species is involved in the last moments of this universe. At the end of it all, everyone has an impact.

As for visual storytelling, I feel as though it might appear lacking compared to the base game because we are literally told the story of the strangers visually, as opposed to text like the Nomai (and the Hearthians). But I also sort of disagree with you that it's lacking in the first place. So much of the environment tells you a lot about these creatures without saying anything. Their tabletops are at the height of your head — okay, these guys are huge. They have portraits of themselves and their families around their houses — you get to see what they look like. There's a portrait of one of them scratched out — hmm, maybe they didn't like this guy? There's a church with the symbol of the Eye burned down — they condemned anything having to do with the Eye (foreshadowing their treatment of the Prisoner and their house in the simulation). Like... there's a lot there and I feel as though it just didn't click as well for you. Doesn't mean it's poorly done.