You bring up good points and none of it is unachievable but it comes down to what kind of game you're trying to make and how you make your images.
It heavily depends on the story you're trying to tell.
If your game contains 3-5 girls and the story is based on just those girls and they're relatively bottled then branching paths make complete sense.
If you're trying to tell a story with a narrative not solely based on the girls and the story calls for many girls that all interact with each other constantly then branching paths balloon into an absolute insane amount of work and an incoherent story.
Let me quickly explain.
A lot of games bottle their characters. Meaning the only interaction is between the MC and the LI. And the LI's never really interact. That allows for way more options as render work and story work remain 1:1.
Now say that character has to interact with three different girls that all have the same amount of options. They also interact within a narrative. You now have to tailor hand renders for attitudes, characteristics, emotions / facial expressions, etc for every single one of those interactions. Meaning the story and work has ballooned into at least 10x more work. Also keep in mind my average render time is 30 minutes, that's after setting up my scene.
Now imagine if I'm trying to tell a story about a guy helping a lot (a lot) of girls. While working within a timeline of a college basketball season where every girl interacts and not just a few at a time. There's absolutely no way for me to include an intricate branching system without me slowing production to a halt. (also my story just doesn't call for it.) Yes some girls will have super detailed story lines while some others will be simpler. The same goes for some decisions, there are some that will change a lot about the story while there are some that don't do much at all. (I'm looking at you "chicken" or "salad") And yes I try my best to have a varied cast but it's not for the sake of making something for everyone. It's because my story calls for a large cast and I wanted it to be varied and have every girl have their own "thing".
Sometimes you just gotta realize what you are and not try to be something you're not. Which is why the walk through is what it is. A big reason for why that "is" is because I started working on WVM because there weren't any games that were made exactly how I wanted. So I made it myself.
You seem to know exactly what you want and have a vision for something so if you have any interest in it then I'd heavily suggest working on a VN / making your own.