Isnt the whole BG3 alchemy Larian homebrewn ?!?
No.
The only real "Homebrew" is Larian's lack of "This is done during a Long Rest over many hours" schtick, which is most notable with "Spell preparation" being done whenever you want.
Prior editions of D&D featured Alchemy, allowing you to brew potions over several hours of long rest by having the ingredients and passing relevant Alchemy checks (With Alchemy being an Intellect based skill)
Herbalism Kits were used to make healing items and could be used without a Long Rest to make Healing Potions, Salves and Soaps.
Alchemist Kits were used during a Long Rest to make Potions, Elixirs and Bombs.
Poisoner Kits were used during a Long Rest to make Poisons, Coatings and Acids.
This is along with other crafting things like Spell Scribing to make Scrolls (Using various checks depending on the spell being scribed - Knowledge, Arcane, Lore or Religion)
Of course, these are not to be confused with the Alchemist, Artillerist, Arcane Bomber or Scroll Savant subclasses (For Artificer and Wizard respectively) wherein they condense magic into potions and bombs (With Scroll Savant simply being better at using Scrolls and magical artifacts rather than being a requirement for spell scribing) which is their version of casting spells.
