While I agree that the option to turn the watched icons off might not be the “best” idea ever, the fact that it’s being asked for means there are people that have a valid use case for it.
Therefor it shouldn’t matter why someone doesn’t want the feature or why they might consider it an “annoyance”. What should matter is how to satisfy their request.
So here’s one way to do it for movies: (This only works for the currently logged in account on the Web App. This works for THAT ACCOUNT and that account only. I don’t think you can do this on most client apps, but might be wrong. Check your preferred client app for the options.)
If you go into list view, (Or any view, for that matter) you should see an icon that looks like a box with a check mark in it. You can use this to tag multiple items. Go to the top of your list, and hit the box, and click on the first one. Then scroll down your list to the bottom, and holding the shift key, click on the last item in your list.
Now you should have a circle with a check mark in it show up on the left, which says “Mark as Watched”. Hit that and sit back and wait as the server marks all of the media as “Watched”.
Now, since all of your current media is marked as “watched” you need to worry about anything you might add, so you can turn this off as well. The beauty is, you can use a similar mechanism for this, but it takes using a filter.
In List View you should see an icon made of three lines. This is titled “options” but it’s really more correctly termed filters. click this, then click “More Filters” and the top on the list there is “Unwatched”. hit that and it shows you everything you’ve added that doesn’t have a “Watched” status. Then just go back and multi-select, and hit the “Mark as Watched” and you’re set.
You can do something similar to TV shows and now you’ve seen it, you should be able to figure that out on your own. (The process is exactly the same.)
HTH