Mojang is moving all of the Java edition accounts over to Microsoft. Doing this will add new layers of protection to your gaming account that Mojang can not offer. If you do not migrate your account to Microsoft you will lose your game.

Here is a link to a FAQ post from Mojang. Minecraft: Java Edition Account Migration FAQ

If you are the owner of a Minecraft: Java Edtion account make sure over the next month you log into your account(s) if you want to keep your game.

I do not play Minecraft as much as I once did but that doesn't mean I still do not want access to my game. One never knows when one needs to kill things, farm for things, or just build something.