I want to have the mod features (like coral sand farming and netherrack generation) in my existing protosky world. It seems like simply adding the mod into your mod folder doesn't do it.

You have to enable the features you want specifically. Use the /carpetskyadditions command and it will list each setting. The datapack is enabled all at once using the datapack command if you want to use that.

Make sure to set it default if you want the change to persist over server restarts.

I don't want to enable cheats. Can you make the external datapack automatically enable these features?

If you just want the default settings (as of 1.19.3-4.2.0), you can just put these two text files in your world folder. Make sure the extension is .conf and not .conf.txt or anything else like that.

carpet.conf

renewableSponges true
piglinsSpawningInBastions true

carpetskyadditions.conf

tallFlowersFromWanderingTrader true
lightningElectrifiesVines true
renewableBuddingAmethysts true
gatewaysSpawnChorus true
renewableHeartsOfTheSea true
renewableDragonHeads true
shulkerSpawnsOnDragonKill true
renewableDiamonds true
rammingWart true
foxesSpawnWithSweetBerriesChance 0.2
poisonousPotatoesConvertSpiders true
saplingsDieOnSand true
renewableEchoShards true
allayableVexes true
coralErosion true
hugeMushroomsSpreadMycelium true
renewableNetherrack true
renewableDeepslate true
renewableSwiftSneak true

Thank you so much.