Before Blizzard rebalanced almost every aspect of Diablo 4 with the launch of season 4, gold wasn't a problem. Now it is and, despite Blizzard already making one change already, players can't agree on what needs to be done next.
Diablo 4 kind of works like an MMORPG. Most things in the game cost gold, like changing the stat on a piece of gear or crafting potions. Part of the reason is to encourage you to earn gold alongside other activities and to keep the game's economy stabilized.
