(Too) Realistic Inventory
Have you ever wondered why vanilla Minecraft allows you to use items from all inventory slots simultaneously? In real life, you only have two hands, and this mod perfectly conveys this realism in gameplay.
With this modification, only one main inventory slot, the off-hand, and equipped armor remain available for immediate use. All other cells become inaccessible for quick application, completely changing resource management and survival strategy in the game.
Now you'll have to carefully think about which items are really necessary to carry with you and which can be left in storage. This adds a completely new level of complexity and realism to the familiar gameplay.

Installation requires Fabric together with Fabric API.