If Clerics want to improve their healing potential, damage output, and more, D&D 5e feats like Chef and Gift of the Gem ...

The Knowledge Domain Cleric gets a revision in the latest Unearthed Arcana playtest, proving once again mind really matters.

To cast a spell, you use a spell slot of the same level (or higher) ... Page 201, Dungeon & Dragons Players Handbook 5th edition. One class whose spell slots don't work this way is the Warlock.