It would be quite hard to implement on that same page indeed, but an alternative could be to 'nudge' people into writing specific reviews from the profile page after you login. Similar to what now is done with the ratings (it shows the sites you have visited but not rated). UPDATE: I see that it is there already, but sorted by number of reviews, lowest first. Maybe I can change that to oldest last review
Will look into it, but have a few other things to do as well (including the twhs overview page).

In the meantime, I have now almost finished moving all my own reviews to the standard review section. Plan to wrap it up today. So the 'last reviewed' dates aren't influenced by that anymore.

I've managed to create a version of the "Unreviewed" page for TWHS, as an inspiration for writing additional reviews where we already don't have many. The list is ordered by 'no review at all' first, there are some 791 of them! That's why the table doesn't seem to show dates at first.

You can find it at: https://www.worldheritagesite.org/ranking/unreviewed+or+unrated+twhs