Initially I tried setting the worldgen to an empty array, but towers still spawned

worldgen {
    # The dimensions that Apotheosis's worldgen will generate in.
    # Server-authoritative.
    # Default: [overworld]
    S:"Generation Dimension Whitelist" <

     >
}

Then I tried adding a dimension mod solely to put the worldgen on that dimension

worldgen {
    # The dimensions that Apotheosis's worldgen will generate in.
    # Server-authoritative.
    # Default: [overworld]
    S:"Generation Dimension Whitelist" <
        solara_dimension:solarademension
     >
}

Still, towers spawned in the overworld

I don't want to make a datapack for this because:

1. on 1.20.1 I could disable the adventure module without disabling the potions module and village module (what I really want)
2. I would not mind some adventure module features, but I don't want any custom worldgen
3. making a datapack to exhaustively remove worldgen by changing the settings on each feature individually would be tedious
4. I have no convenient means of loading datapacks (by default, as in a pack configuration), I tried loading the datapack from #1021 using a few different approaches and they did not work, not to mention that only applies to towers (and see point 3, I'm not going to extend it myself).

I also tried opening up the jar and ripping out the worldgen folder, which just prevents world creation entirely.

The generation whitelist only impacts features (Boss Dungeons and Rogue spawners); towers use Minecraft's Jigsaw structure system, so they can only be configured through datapacks.

on 1.20.1 I could disable the adventure module without disabling the potions module and village module (what I really want)

The Potion and Village module have basically died and been scattered in the wind. You can elect to disable the Adventure Module by uninstalling Apotheosis, but Potion Charms are part of this module now (The potions themselves are part of Apothic Attributes), and the Wandering Trader trades are part of this module as well.

I would not mind some adventure module features, but I don't want any custom worldgen

If you want to disable the towers entirely, the easiest solution is to datapack these biome tags to be empty, which will reduce the spawn pool to zero. You should also be able to use KubeJS to zero out the tags, if you're more familiar with KJS syntax.

making a datapack to exhaustively remove worldgen by changing the settings on each feature individually would be tedious

Well, it works for all the features, so that's more than half of the 10 files you would need to edit anyway. Hardly "tedious" imo, though certainly more annoying than flipping a config switch.

I have no convenient means of loading datapacks (by default, as in a pack configuration)

KubeJS, Open Loader, Global Packs, et. al. will allow you to load datapacks on a per-modpack basis. That specific datapack doesn't work well with those mods because it relies on a pack.mcmeta filter, which I think only works when loaded in the world selection screen or something of that sort. I generally don't recommend using mcmeta filters for that reason. They're more like a sledgehammer.

That's ok, in my case I didn't care about the potion charms, but the potion recipes, so that's good, but what about the fletching system?

I will uninstall Apotheosis for now and just have the Enchanting and Spawners mods.

For your consideration, here's what I was trying to achieve in total:

• keep all of Enchanting and Spawners and Potions (but don't care if potion charms are in or not)
• remove all worldgen from Adventure
• keep the random boss spawns from Adventure (don't care if the changes to dungeon loot are in or not)
• keep the salvaging and reforging system from Adventure (and extend it with some addons too)
• keep the fletching from Village (but I don't care about the wandering trader)
• remove the features from Garden (but I'm assuming that's not in anymore either, I like the ender lead though)

Fletching was removed in 1.21 with the end of the Village Module; it wasn't a compelling enough feature to keep on it's own, and it wasn't a well-suited feature to integrate into any of the other modules. Overall it was a pretty unsuccessful feature, seeing only very niche usage (if any) over its 6-year lifespan.

The functionality from the Garden Module is largely replicated by Configurable Cane. The Ender Lead recently made it back into Apothic Enchanting, so that's still around.

keep the random boss spawns from Adventure (don't care if the changes to dungeon loot are in or not)
keep the salvaging and reforging system from Adventure (and extend it with some addons too)

You will need the main Apotheosis installed if you want to achieve those goals, though.

You will need the main Apotheosis installed if you want to achieve those goals, though.

Yes, well that's why I wanted to remove the worldgen in the first place, but making a datapack to do it is not worth it.