While I believe this is especially true in Limited, in formats like Cube Draft particularly, where, while a card like Garruk Wildspeaker is the better card in your deck, you still may need a card like Acidic Slime
Conclusion I do want to basically sidestep the argument over whether or not all planeswalkers should be commanders: Myth Realized is doing a good job getting into what the format could be like with them involved
Youll be able to reanimate a creature, fill your graveyard some more, and get a free 5/5
For example, Natures Lore is one of the best ramp spells of all time, and Brainstorm and Necropotence are two of the best card draw effects of all time
For example, Fires of Invention in Pioneer has a naturally high curve that allows the deck to run Keruga for free