The bug

In previous versions, entities would continue to render on the death screen, when the player has died and is deciding whether to respawn. This last worked correctly in 21w16a. Over the next few snapshots, entities would briefly flicker after death but ultimately kept rendering. Finally, in version 1.17-pre1, entities would disappear and not return. This issue has persisted since then.

Impact

It looks as though your dropped items, and possibly the enemies that killed you, simply despawned, even though they didn't.

How to reproduce

1. Fill your inventory with items
2. Spawn some mobs nearby
3. /kill

Expected behavior
The entities should continue rendering while you wait, dead.

Observed behavior
After a moment, all the entities disappear. They continue to make sounds, if applicable.