Diablo 4 Gold can help with general gearing costs, but Season 15 puts more emphasis on making the most of the items you already have. Season of Hell's Legacy changes Mythic Unique crafting by allowing players to turn a carefully upgraded Unique into its Mythic version without throwing away the work invested in it.
This is especially useful for endgame builds where one specific Unique is essential to the setup.
Three Ways To Craft Mythic Uniques