I like the new Achievements UI in Endwalker, however there are a few things I would like to be improved.

When I have completed an achievement with a reward that I have yet to claim, this should be obvious to me as a player. Right now it isn't. I must regularly check the window and browse all of the categories to look up if I have any unclaimed rewards. This process is extremely tedious. You could implement a special tab that would only show unclaimed rewards, or place UI notifications next to achievement categories that have unclaimed rewards.

It is hard to differentiate between achievements that I have completed and that I have yet to complete. You can feel this in particular when you are scrolling through achievements at a somewhat faster pace and trying to look up what you're missing. This insufficient differentiation makes it really unpleasant to browse achievements frequently, which detracts me from caring about the feature altogether.