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. In the last three seasons, as long as you weren't risking it all on rerolling stats, gold wasn't a problem.
But now, simply upgrading a low-level piece of gear with a Legendary power, or aspect, can cost hundreds of thousands of gold each, preventing you from swapping your build around as freely as before.
Endgame players delving into The Pit, Diablo 4's new set of increasingly difficult dungeons, have it even worse. The whole point of doing The Pit is to earn crafting materials to upgrade your items with Masterworking so you're strong enough to do higher levels of it.