But I never got on the 3e bandwagon and so I always thought even OSR games took too long. It largely boiled down to a thought I had one day "What the hell IS a hit die anyways?".
I wanted the ability to fully flesh out a region (and any dungeons or ruins in it) as fast as I could think them up. But I also don't want everything to be generic. I don't want to save time by slotting everyone down as "mook or evil boss #1 reskinned". So I didn't build Neoclassical Geek Revival to do that.
When it comes to adventuring, everything in Neoclassical Geek Revival is descriptive. You describe "stat" things only as you need them, and purely based on description. So lets say the party runs into goblins.
I start with an average man, all 10.5's for attributes. I will need the following chart from page 24 of the lion printing.
Task is considered:
Very simple +10
Utterly trivial +20
So I start off by thinking "How is this goblin different from a person?" I might be tempted to say "Weak" and lower the the strength. I would say "An arm wrestle with a goblin would be easy" so I give the goblin -5 strength. I round down if the total is below 11 and round up otherwise (personal quirk). But is the goblin really "weak", compared to a man sure, but a man is twice as big. This wouldn't scale right if I did that. So I use the "Size modifier rules" (page 39 in lion printing). So the goblin is half the size of a man in my mind, he is size modifier 1/2.
So that means I am comparing a goblin to a man shrunk to half size. I don't see him as especially weak, but I would see him as very crass (-5 social) and somewhat quick (+2 agility) and otherwise as a man.
So thus far the goblin is all 10's, except for 5 social and 13 agility (if it ever comes up). The goblin is also size modifier 1/2 (all damage he deals is halved, all damage he takes is doubled. For stealth all suspicion he takes is halved and all that he deals is doubled). Nothing written ahead of time other than "12 Furitive, Ill Tempered Goblin hunters with hide shields and javelins"
So what about their equipment? Well I would say that for their size, the javelin is a medium weapon (check) that does piercing damage (check) and then throw on some weapon tags like "Pole weapon" and "Throwing". I would say they have large shields, but being hide they have the "Light" tag. This is all in the equipment setting.
So the light shield is giving them +4 to defense (can't stop armour piercing or devastating weapons), and the javelin is doing d6 repeating damage, with +2 to hit when thrown, a range of 2 areas, and -2 to hit in melee. All of these are size modifier 1/2 (like the goblin). Finally they don't have names so they are 0th level. They are hunters, so their 2 "class" pie pieces would probably be warrior (specialist in javelins since they are hunters not warriors) and rogue (specializing in tracking).
Let me show another example.
Maybe I right "Ginormous but lazy fire breathing dragon named Guams"
So how many times bigger than a man is this? 10? Sure, it is size modifier 10.
So I see it as insanely alert (20 awareness) and very clever (16 intelligence) but maybe somewhat old, arthiritisy and unhealthy (8 agility and health).
It has scales (mail armour), made of dragon (material if you care). But it has an exposed belly so I'd give it's natural armour the "Partial" tag.
It's claws (if they get used) I'd quickly think of what they count as. So they are small (to the dragon) but slashing weapons, probably count them as "vicious" too. So they do a d6+1 damage if they hit (x10 for size). If the dragon bites I might apply different tags, same with the tail. For the tail I might call it a large, blunt weapon (d8 x 10 damage).
It also breathes fire. That seems magical so I sort through a spell to look for an appropriate one. "Cone" seems to be a suitable template, its a size modifier 10 creature so I say it has enough mana to cast it at power level 10". I'd count that as an innate spell, same as an "elf" with its cantrips. I could do the same with any other abilities.
It has a name, so finally I'd give it a level and class, I think I'd pick warrior and bard (it likes riddles) and give it "Dual wield" (I see it hitting with both claws) for warrior, and for its two part bard i'd give it ("Reputation", "Silver Tongue" and "Wit"). This is based on viewing Guams as a retired warrior who couldn't hold his own against another dragon, but sure has a fierce reputation among dumb peasants. Since I haven't written down any notable deeds Guams has done, that means he's on his first milestone, and thus level 1.
Both of those are "Just in Time" mechanical explanations to the creatures when they come up. They can be placed ahead of time, but the mechanics themselves don't need copying down.
This also applies to traps, magical items, etc. With people who have skills, they use the same "schrodinger's character" mechanism as new PC's. I just assume that most of their skills aren't applicable to the current situation, but 1/3 of their intelligence worth will be (usually 3).
For some things you will want to write down specific details, if a wizard has specific spells, write down their names (you can use a spell template to add the appropriate mechanics). Jot down how pious a priest is.
But in general, most things just be descriptive about what is in a location. Thus when it comes to modules, Neoclassical Geek Revival is truly system neutral.