Blizzard has just released a developer update video chockful of updates coming to Diablo 4 Vessel of Hatred, one of which changes World Tiers in a way some may not have expected. Throughout the video, the developers discuss the changes coming which are based on player feedback, but the most eye-catching change is the removal of World Tiers, a system added with Diablo IV that required players to unlock higher difficulty levels before bringing their characters into them.

https://screenrant.com/diablo-4-vessel-of-hatred-developer-update/