After reaching level 100, common, uncommon, and rare chests become useless for most players.
To make them usable, I thought of a new solution: combining weapons and reforging them into new, better weapons. For example:
1 common chest = 1 common weapon | 5 common weapons can be combined to become an uncommon weapon.
1 uncommon chest = 1 uncommon weapon | 5 uncommon weapons can be combined to become a rare weapon.
1 rare chest = 1 rare weapon | 5 rare weapons can be combined to become a legendary weapon.
The 5 weapons need to be of the same type to be combined (the modifiers don't matter, and with each weapon reforging, subsequent modifiers would be random).
Imagine you're trying to get a bow for the ranger, but you can only get swords in the legendary chest; instead, you can open several cheaper chests and "assemble" your bow in small parts. This requires more effort, but it can benefit casual players with a sense of progression.
For this to work, the inventory would also need to be expanded, along with the idea suggested by Mako: "Group chests into counter like stackables rather than individual items."
*Please change the price of the uncommon chest to 5k gold for perfectionist purposes