That’s not normal behavior and sounds like something is corrupted for the character or account.
I often see players mentioned that they did “everything,” but unless you tell us what “everything” means to you… it’s very difficult to know where to start or how to help you.
Most people forget to reset Cvars when resetting the UI. They also forget to do the basic steps like forcing Windows updates or clean installing their drivers.
It’s definitely playable. Tech Support is where people go to complain about issues, so that’s certainly all you’ll see here. But while a small amount (yes, even thousands is a very small amount) may run into issues, hundreds of thousands are playing without encountering any of those.
The biggest issues are half-troubleshooting or hanging onto config files or addons because players don’t want to rebuild their UI. Unfortunately, any addon can be a source of problems. Blizzard doesn’t check them for issues, only for adhering to game rules.