Ah fuck it. I'll double-post, because this shit grinds my gears...
Why are there no YT channels out there that teach people the fundamentals of miniature painting? The only one that comes close is Vince Venturella (pbuh). I've been half-tempted to make some videos myself, because if you're just coming into the hobby and/or going beyond the absolute basics your options are i) watch somebody paint a Golden Daemon winner or ii) some variation of slopchop/how to paint a 2000pt army in five minutes.
I'm no expert, but I've accumulated enough knowledge over the years to know that there are huge gaps out there. Simple shit like how to thin paint properly for the type of application you're using it for, how to apply it based on what you're trying to achieve, what techniques to use at each stage etc. The scale modelling channels seem to have this covered, but most miniature painting channels are either trying to hawk the latest paint or are just a self-congratulatory wankfest. There is a bunch of stuff that is just assumed and people wonder why they can't re-create what they see on screen, get disappointed and ultimately feel less inclined to take part in one of the most rewarding aspects of the hobby.
I've seen a few channels cover basics pretty well, but the problem is that content already exists and rarely does anyone have anything meaningful to add to it so it doesn't attract a continued viewerbase and thus the channel dies or usually starts with the clickbait bullshit.
A channel that comes to mind that tried to keep with basics and failed, would be Doctor Faust's Painting Clinic.
You can see that his channel was doing pretty decent... 10 years ago and then it basically died. He still posts videos, but no one wants to watch it. There's only so many times someone is going to be willing to watch someone show you how to thin paint, do glazing, paint eyes, etc.
Kujo Painting is another channel that comes to mind, that never took off and hasn't posted in months now(not surprising)
Apparently people took issue with some of his jokes in videos and complained about them rather than focusing on the real content itself from what I recall.
Hilariously while the slapchop shit content gets the views, what most of them aren't actually showing is
a: They never actually paint entire armies anyway(this is also a thing with channels where they love to show spending 37 hours on every single individual fucking space marine)
b: They don't show the 2-4 hours of fixing the fuckups with the slapchop shit to correct mistakes making the entire thing a waste of time if you're doing anything that isn't mostly organic(shit like tyranids, kroot, stuff like that) where you'd never be concerned about bleedover from eye lenses/cables/holsters/whatever onto another surface anyway
Zumikito actually covers the slapchop crap well(as in truthfully), but he's also a retard who throws tantrums when he doesn't win painting competitions, bitching about how many hundreds of hours he put into what amounts to good work but not good enough to win a GD. But he also doesn't focus on the basics, because the basics haven't changed in years and there's just no point.
https://www.youtube.com/@Zumikito/videos
Marco Frisoni as mentioned doesn't do basics, but he shows how advanced techniques can actually be done in an amount of time anyone could call quick.
Everyone knows the "thin you paints" mantra, but even something as fundamental as thinning your paints doesn't come naturally and it is something that comes with it's own set of nuances. Paints thin differently depending on the pigments used and their density, some paints are more prone to chalking when thinned, different manufacturers use different mediums which adds another layer of complexity to it etc. Sure, you could just blunder through it and use trial and error, but knowing what to look out for would stop a lot of disappointment and stripped models.
And this is a key problem with videos about thinning paints. People love to mention "thin your paints till they're the consistency of milk" no one on the fucking planet is familiar with moving around milk with a brush on a palette, and as you point out that's not even a good comparison if it were somehow true because it's going to vary vastly between paint brands/lines at times. Scale75 has a more gel like consistency which isn't going to thin the same as AK 3rd gen, which isn't going to thin the same as Vallejo metal color, and so on. Even beyond that, sometimes thinning paints may not even be the "correct" thing to do, and it also varies a lot based on personal preference just on how you work. Hell, here's Vince Venturella in a video about painting white discussing using unthinned heavy body acrylics on a mini
The basic information is out there and readily available(anyone trying to get into painting now is far better off than they would have been 20 years ago), but no youtube channel has anything to gain by trying to focus on it. Eventually people just need to put paint on a damned mini themselves so they can get a feel for it and understand the things that these channels discuss and show in videos.
Edit: What you probably also don't want, is an entire channel mostly dedicated to drybrushing(a basic technique that has its uses) and stippling(also has its uses) that really only exists to shill their fucking overpriced $200 sets of goat hair mop brushes you can find for $5-10 a piece easily at a real art store or even in cheap $30 sets on amazon(that also come with a cheap wood box).