For example, rather than introduce an entirely new class or subclass, my approach is to have Witch be a background. This is a background that works similar to the backgrounds introduced in the Guildmaster's Guide to Ravnica, where it gives you an expanded spell list, and in that spell list there are the iconic witch spells like hex, find familiar, magic circle and so on (bestow curse isn't in there, since that would break the Warlock class). This allows my players to approach witches from a very broad range of directions. One players could be a more academically minded witch and use the wizard class. Another can be a more wiccan inspired witch and use the druid class. Another can be a dark witch and be a fiend warlock. They can even, if they feel really creative, be some sort of witch paladin.
The background also unlocks unique feats that I'm still trying to iron out. Like being able to make your own weird magic items, a unique form of fortune telling, and the ability to form a coven with other spellcasters.