@Psiren_East You could try simply deleting the Legacy Edition data within the game's program files. Make sure Origin isn't set to automatically update your games (Application Settings > Application > Client update), or it'll redownload the LE either the next time you open Origin or the next time you launch the game.
If that doesn't fix the issue, you could try uninstalling Sims 4 and reinstalling without the LE. In this case, Origin will likely try to reinstall the LE files when you launch the game even if you have auto updates disabled, so as soon as you do launch it, alt-tab to Origin and cancel the download. Origin may also try to reinstall the LE after a game update.
The only way to ensure the LE never installs again is to have someone from EA customer support remove it from your account; that's not something you can do from your end.
You could also try putting Origin in offline mode before you play. I don't know enough about this particular issue to know whether it would prevent the PC from losing its network connection, but it's easy enough to try.
