Steps to reproduce: 1. Create a new world in creative mode.

2. Switch to adventure mode using the gamemode switcher.

3. Switch to spectator mode the same way.

4. Switch back to adventure, and kill yourself.

5. Respawn and try the switcher, it will default to creative, not the last gamemode, spectator.

I tested the bug in 20w20a, the version the gamemode switcher was added in, and the bug was not present.