Ask someone what is wrong with their pantry and they will say it is too small. Then they will find three open bags of the same rice at the back of it. The shelf was never the constraint.
There are three things that make a pantry unreadable, and they are worth fixing in order, because the first one is what makes the others visible.
Bags and boxes that will not stack
A half-open bag of flour takes up more room than the flour does, and it cannot have anything put on top of it. That is two losses from one item. Square airtight containers fix both: they stack flat, and because they are clear you can read the level without picking anything up.
Where people go wrong is buying four containers to try the idea. Four containers do not change a pantry, they just add a fourth thing that does not match. The 10-piece OXO POP set is enough to do one shelf properly and find out whether the system suits you. If you already know it does, the 20-piece set does the whole room in one purchase, which is the version I would actually recommend to anyone doing a full reset. Buying the small set twice costs more than buying the large one once.
If you would rather have containers on show than hidden behind a door, the ComSaf glass jars with bamboo lids are the same principle in a material you do not mind looking at.
The back of the shelf you never reach
Deep shelves are the second problem, and no container fixes them. Depth is only useful if you can get to it, and the honest answer is that you cannot reach past about thirty centimetres without taking out whatever is in front.
A turntable converts depth into rotation. The Lamu two-tier lazy susan gives you two levels of it, which suits spice jars and oil bottles, the things that multiply fastest and hide best.
For the loose packets that will not stand up on a turntable, sauce sachets, stock cubes, snack bars, the Vtopmart clear bins split a shelf into pull-out zones. The bin comes to you; you do not go into the shelf.
Leftovers in mismatched tubs
The fridge version of the same problem. Mismatched containers cost you space twice, once because they do not stack and again because you keep lids whose bases are long gone.
Rubbermaid Brilliance is the practical choice: clear, leak-proof, made to stack. Pyrex Simply Store is the one to pick if you reheat straight from the fridge and would rather not put plastic in the oven.
The upgrade almost nobody makes
If your pantry is genuinely full and you have done all of the above, there is one more move: stop storing air. A vacuum sealer flattens bulky bags of rice, pasta and dried fruit so they stack like books instead of slumping like beanbags. In a small pantry that is the cheapest square metre you will ever buy, and it keeps things edible far longer as a side effect.