This thread was useful. Basically the “Watchlist” doesn’t do what people think it should do, and there isn’t an option in settings to change that so that it will. Creating a personal list and then filtering the results to hide Watched is seemingly the only option when it comes to lists.
Then there’s “Progress,” that that again requires that you change the sort order because the default of “recently watched” isn’t all that useful. Edit: I see there is a setting for that!