The best one I know of is JustWatch. Its an app you can install on your Phone or on your Smart TV. It tracks TV & Movies you have or haven't watched and you can simply ✅ them off as you watch them. There's a free version and a paid version. You can mark off entire season's in one go if you've seen them instead of episode by episode. It's available on the Google Apps or iPhone store

When you get to my age it's the other way round 🤣🤣