[2020] Long load times, unplayable. Refresh?

If you want to reset things back to how a fresh game would be, you will need to unsubcribe from everything. All your workshop subscriptions come back when you reinstall the game. They need to be removed to start fresh.

You can do that in game by going to the Content Manager, then all the way to the bottom pick the category Steam Workshop. It has an Unsubscribe All button. Keep in mind that it might have a while for it to unsubscribe everything, so be patient. And once it's done, you will want to restart the game.