I changed my Java display name, and tried logging into my world, however, I was at the world spawn, had nothing in my inventory, and was using a default skin. I tried reopening the game, and the issue persisted. It was only when I relaunched the minecraft launcher that the issue was fixed

I expected that the launcher would update with my new player name, and I would be able to continue playing

I think what actually happened was that the minecraft servers updated, so that the player by my new name had all of the player data on my world, but the minecraft launcher was still detecting my old player name, so it recognized me as a different player and did not retain the player data until i relaunched the launcher, updating it to my new name.

steps;

1. open minecraft launcher
2. change java edition display name
3. do not close the launcher
4. launch minecraft
5. the game will recognize you as a different player