> I understand there are many factors that come into play such as lighting, time of day, exposure, etc.
Yes, absolutely.
> I use the same camera + lens and make sure to have a consistent white balance of around 5,600K. Overall, I am really trying my best to keep everything the same as much as I can in camera for all of my sessions.
Here’s your problem: you know there are a ton of factors that impact your image, but you’re keeping everything the same in camera.
It may help for you to understand the inverse square law. Briefly, the as you increase the distance between the light source and the subject, you lose more lighting than you would expect. Double the distance means your light is only one quarter as powerful. And that matters more than you would think.
> In theory, shouldn’t my RAW images be somewhat consistent-ish? Obviously not identical, but basically in the same realm?
Nope, because you have zero control over the direction and quality of light when you’re shooting natural light.
My advice to you, if you want consistent shots, is to start working with off-camera flash. You will also use ambient natural light. Well-executed flash balances with ambient, and won’t come across as “flash” to your clients.
The best book I’ve ever read on flash portraiture is Direction and Quality of Light by Neil van Niekerk. You can get it used for under $10.