If you're making a game, dont start by thinking about your inventory system. Start by thinking about what you want your player to be able to DO, the cost of those things, and the constraints.

For example, ages of empires didnt have you worrying about unit equipment at all. every villager could do almost any job. while survival games, especially survival horror, like the recent RE remake, severly restrict inventory and stack sizes to make resource managenent more important.

Games like Fallout had list based inventories because lists are cheap, and it allowed a tighter interaction loop. players would loot. go into inventory. close container, onto the next container, keeping the player in the exploration loop longer. neoscav did the opposite *for effect* harkening back to diablo, but taken to the nth degree: *everything*, actions, combat, exploration, character design, all based on an inventory-style grid.
while games like rimworld and dwarf fortress have your inventory represented by zones where items are physically *stored* in stacks on the ground, extending the concept of base management to resource management through physical layout and build optimization.

its important to think about what kind of actions you want players to be able to do, and the kinds of challenges and constraints you want on them at each point of the game and each mechanic they engage in.

other examples, though terrible, include fortnite, where the limitations of competitive play had inventory limited to a resource system and a hotbar. while earlier battle royale and sandboxs games like rust and battleground induced tension by combining loot mechanics and grid inventories with the constant danger of competing players, allowing them to have richer inventory systems at the risk of frusterating players who frequently died while managing their inventory. meanwhile in overwatch, notice how the HUD changes to best represent the abilities of each character.

all in all it is better to stop thinking of inventory systems as a means to an end, and instead as the end representation of desired mechanics, or artificially selected representations for particular effects.

this applies likewise to ui and ux in general. because the design of interface is fundementally about the design of *interactions*, and what you want to enable a user or customer to *do* will ultimately drive those interactions.