Keeping magic tucked away into the corners of the Earth is not exactly what I'd call realism in a scenario where a level-0 farmhand can cast magic missile if he ever just decides to start an adventuring career.
Making a consistent world is a task, no doubt.
With regards to this, I think we want to remember that most folks are level-0....adventurers are still nobodies at level-1, but are just a bit special because of their training. A magic-user has been taken under the wing of a mage, trained for years to learn magic, giving an expensive spellbook of his/her own (VERY expensive...something like 5-10 years of farm-hand wages), and sent off into the world. Likewise, clerics are of a very small minority that have been gifted by the gods to perform miracles. Fighters least-unique at level-1---are still probably the most dangerous (they CAN survive a sword attack...most peasants don't).
Don't sweep this under the table. That's one of the first steps in not screwing your game up.
It is part of what makes 2e suck (Prince's excellent return to the thread topic), that this gets forgotten. PC abilities are normalized, as is Magic (reliable and ubiquitous like technology). So now that you've decided the once-special is now common-place, you're left with two options:
a) hand wave it, and start looking for EVEN MORE easily obtained "skills" to keep your PC/campaign interesting (ability inflation)
b) think through what that does to society/civilization --- and try to (re)build a whole stable game/world (as you suggest)
If you choose (a), you get suck-y 2e.
If you choose (b) then, like Late 1980's/1990's comic books who went through this identical deconstructionist phase (
"What if superheroes really existed in our world?"...oooh...shock!...awe!...death-spiral into nasty edge-lord crap), you have your work cut out for you...but then you're moving away (out of boredom?) from the known and into the unknown---something that's not really D&D, but your own thing.
(As an aside, once the MCU and CGI made $uperhero$ work on-$creen, it was inevitable the next-phase deconstructionists would also arrive: e.g.
The Boys,
Umbrella Academy, etc.---spoiler alert: superheroes with tons of mental/emotional problems doesn't end well. Kinda ruins the whole genre. i.e. bad romance novels or sick psycho-drama.)
To my mind, everything you are suggesting has been tried. Your logic seems solid, but the place it ultimately takes you is not one I care to visit (again). I'm sure that you think:
"It's different for me. I'm not an idiot. I'll pull it off. Any concern you raise, I'll instantly think of a solution..and that's what I'll claim I'd do." --- well, maybe...new things happen.
But what I find a more reliable foundation on which to build is look back over 40 years of D&D, and learn from the mistakes, and also what has been proven to work. Make good notes of each, ask others for suggestion based on their experiences...and then use knowledge-gained to improve your game, seeing what works for you. Don't just sit there self-content thinking you've got the Perfect Table Experience (sing it!
"Ain't nobody gonna' tell me nothin'...Can't tell me nothin'..."). EOTB (and others) have opened my eyes repeatedly to game-balancing elements that were not obvious to me originally. Cause and effect. Balance matters (...and we are such stupid, short-sighted animals).
That's not to say you can't innovate. But as someone who struggles daily with the bleeding edge of engineering, let me tell you---the improvements you can make are usually
tiny, and you don't know for a long time if they are actually better vs. just
different. Edison's rule of 99 failures to one success (IF you are exceptionally good at what you do). But if you don't bother to
really understand what others have learned before you and become proficient at applying it, then you are going to look like a cocky little fool and almost certainly fail big.
Those who don't learn the lessons of history,...
10 out of 10 points for Style, but...
etc.
When Gygax and friends were ousted from TSR, they were the folks with the most play/rules-creation experience. It seems pretty clear their replacements (who where attracted to a nerd-hobby by the smell of money), had no concept of how all the piece went together. No history with what had worked/was-broken with OD&D. Balance LOST...and the game immediately started going off the rails:
hence this thread.
History hath pronounced it's judgement:
2e doth suck-eth.
(...and excessive normalized/quantified/categorized/standardized magic was part of the reason why)