Shinra HQ is simplistic in the OG, but it wasn't the final boss area in the OG. There was so much room for expansion, where the crew has to sneak in, getting keycards one by one by running sidequests pretending to be employees, getting to know people and departments and doing favours until they got the next one, or going through the floor where everyone's gone home except security drones to break into the office where the next one is.We could've, you know, broken into offices and read files, got a real sense of the building and how it worked.
...Why would the heroes be fraternizing with employees and rummaging through offices when their entire mission and purpose for breaking into the most dangerous and heavily guarded location in Midgar,
is rescuing Aerith and getting out with as little attention as possible? What you're saying doesn't even line up with the story. Cloud and the others are trying to remain as incognito as possible. They're suspicious intruders given their appearance and non-professional attire. The only reason they are able to infiltrate as far as they can is due to assistance on the inside and chaos from the plate fall. Because without it, it'd be non-stop battle after battle.
Given the context of the narrative, the pacing of the story, and in-character motivations of everyone involved, you do see a lot of the Shinra Building. You hear the employees and what they're feeling at the time. You overhear conversations with loved ones, anxieties over the future, and watch them attentively listen to an interview with Heidegger over security. I have no idea what you're even looking for because you see and hear the employees in numerous situations and scenarios, from break in to searching for the AVALANCHE informant. You see some sleeping, you find one having a panic attack, you hear them conversating amongst themselves over food, and can even hear them warning each other over asking too many questions.
You get to see their friggin' Combat Simulator and science division. You can spy on the individual employees on the executive meeting floor by peeping through the vents. You overhear how the higher up Shinra Employees deal with the chaos and confusion amongst themselves. Nevermind the Combat Simulator, the Drum, and all of the visual expansion and call backs to Shinra's previous research projects that are seen all around you. Any further, and you strain the credibility of the plot. There are limits that if broken, would cause the story's pacing to simply break apart if you just completely given carte blanch freedom to pretend you belonged in the Shinra Building and made the story one that injects too much gameplay mechanics and openness. It's the most dangerous location for the heroes to be. It's not a place to just chill and have fun.
In ch 7, Airbuster's encounter gets deflated by the quests to disable it in advance. If they really wanted to crank things up, how about a multi stage encounter where it's hunting you through the corridors? Even if they win, the victory might feel more earned.
Because the entire premise of the Airbuster lead up was that it was a killing machine that was being created to summarily execute you on live television, however you had the opportunity to specifically sabotage it's 3 core functions in order to give yourself an edge in battle. Thereby tailoring your fighting experience to one that is unique and structured to your fighting style, making it more immersive and engaging. Having it be a repetitive boss that just keeps coming back for more like the X-ATM092 Black Widow from FFVIII would completely ruin the entire premise and unique battle experience that you're able to create by systematically sabotaging the creation. It's a creative and unique way to literally give the finger to Shinra and create a unique battle experience adjusted to your style.
What you're asking for would be one of the most often seen tropes in JRPG boss battles which would have added zero distinctiveness and identity to one of the most basic and forgettable FFVII bosses. The Remake goes out of its way to make the beginning Midgar bosses unique, intimidating threats that have their own special circumstance and strategy to take down. Making them become more like rote typical boss battles, strips them of what the Remake did right to differentiate them. I'm really not sure why anyone would want such a by-the-book portrayal.
For a similar scene involving mowing down people on a motorcycle was a thing, there's Snow's rescue in Palompolum in XIII. The soldiers get varied responses and seem human, it's a genuine unexpected 'oh crap' ambush of Light and Hope that isn't deflated by sidequests disabling the machines first, and we get to see how powerful the crew is, but there's also a sense of genuine menace and pressure, and the attack isn't played for slapstick at any point.
I can't believe you're even making this comparison....
I
love FFXIII and the badassery that was demonstrated by Snow riding in on Shiva, but to somehow equate
that as having more enemy grunt differentiation and characterization, compared to the actual bike escape sequence of the FFVII Remake is mind-boggling. I have no idea what you're even talking about because
none of the Psi-Com troops say a
thing in that scene. They get blown up.
My mistake. They say two words.
"Open fire."
Now, Yagg-Rosch speaks, and he dehumanizes the L'Cie to his troops, saying they're nothing but targets, while the announcer on the giant tele previously stated that they'll be executing the L'Cie on live television. After Snow subsequently beats everyone, Yagg orders his troops to take them up and out of danger.
There are no varied responses from the Psi-Com soldiers. They say two words.
Not even during the confrontation where Snow marches out of Hope's house while still injured appeals to their humanity, stating that they were all part of Cocoon before being branded L'Cie and that it's just as much their home now as theirs. Yagg-Rosch steps forwards, introduces himself, and coldly but clearly explains the Sanctum's rationale for executing them as threats to the safety and order of Cocoon.
Compare that to scene where Cloud throws his sword inches from the grunt's head as a silent warning. Giving that one grunt a chance to not die for a worthless cause and just run away with his life. That scene alone, with the grunt contemplating his decisions and then running the hell away, with Cloud showing him
mercy, gives more personality to the Shinra Infantrymen, than all of Chapter 7 of FFXIII gave the Psi-Com troopers.
I don't know if you just misremembered something or what, but that comparison is way off base.
The OG had the shock twist factor that worked for it, so I don't think this level of focus on the grunts would have as much place. However, going into remake knowing about Cloud's identity, I thought the scenes with the infantrymen created some nice dramatic tension. I was glad how it made them feel more human from the get go, rather than just a random battle. I started the game immediately feeling bad mowing them down. I didn't think it was really meant to be comic relief, per se. Maybe props to highlight how cartoonishly awful their bosses are, but I personally enjoyed the cartoonishness of Heidegger and Scarlet so... 
