(Warning: A little rant about spellcasters)
Thank you for your warning

(I certainly won't chastise you for going on a rant - especially since I have ranted plenty myself in this very thread

)
Realized I'm tired and perhaps a bit rambly, so warnings for that I guess...
Just wanted to make sure you realized that my comments were made in the context of agreeing this is a lightly-skinned game of D&D rather than a thoroughly reconfigured S&S game that just happens to use 5E as its base.
That is, assuming we just agreed the details of Bard or Druid or whatever is secondary to "it's still D&D", then it stands to reason we can argue Fireball should remain in the arcane casters' repertoires since it represents a significant aspect of these classes.
That is, as a designer, choose which is the more important aspect: class balance (the "it's still D&D so who cares if the Druid can use elemental magic" school) or setting fidelity (which then begs the question why any number of D&Dism aren't removed).
I guess my point is: at the end of the day, Fireball is just D&Ds way to help some classes matter. It can't actually help the players bypass the challenges that D&D would call "low level" (castle walls, deserts w/o water, ...) It just means the caster's ability to meaningfully contribute and share in the spotlight is retained.
Don't get me wrong - I am absolutely on board with the idea that lots of magic stuff should be excised from the game. Heck, I'm even miffed a 5E caster can apply fire (or cold, force, acid) damage each round, every round all day long! That is, infinite cantrips, that logically would allow you to burn holes in any wooden wall, dissolve a murder victim (no evidence) and a lot of stuff that definitely isn't in the S&S ball park!
Personally I would be okay with that as a player, but I know many people who get a lot of enjoyment out of counting every single coin after looting fallen enemies, and spending said (exactly counted) coin on various stuff after the adventure. So I think each group (GM and players) has to come up with a solution that maximizes their fun.
Yet you decide for them Fireball is where you draw the line
Anyway, maybe you already understood this, but to be sure:
I wasn't arguing "regular economy admin should be disallowed".
I was arguing "your sole rules option re: wealth should probably not be nearly as detailed".
Counting every penny is fine, and then spending them on fine wine, or luxurious golden dresses. Downtime activities of Xanathar. Whatever.
It's just that the included rules option doesn't really change all that much. Having to pay 4000 gold for an ability increase or AC bonus
still means having to count all that money.
I find it more useful to, as my sole Treasure Should Be Spent option, present a true alternative to counting money.
If you like counting money, all the power to you. You're likely fine with rules as written.
It is if you really agree Treasure Should Be Spent you might need a rules option that FREES you from bean-counting.
Best Regards
PS. Plus I find I don't really like the option that much. In fact, I think it reminds me way too much of d20 and Pathfinder. I would much rather keep the ability score increases free every four levels, just like 5E RAW, if you ask me.
And that's coming from someone who really likes being able to purchase magic items in my regular D&D. It's just that first you say "In a world without magic items for sale..." and then IMMEDIATELY offers bonuses for sale
"...they need something else to spend their gold on"
In d20/PF you needed this to stay relevant as a character, against high level monsters. In 5E you don't. You simply don't.
In all of D&D you do need things to spend gold on, or gold becomes "worthless". One option is to spend gold on xp, but you've decided against spending space in your document on that alternative.
So my proposal was realize some people are fine with what 5E offers as "gold outlets": which mainly is downtime or even "not much at all". You don't have to focus on providing more options here.
Instead why not offer an option that takes gold-counting out of the equation entirely?
