filming Game Of Thrones started 7-8 years ago, therefore the characters changed a lot across all seasons.
Many of them changed due to aging or character development and that’s, of course, the ones who survived 7 seasons.
Another thing the first season was summer and winter was coming, so the light was bright, however, last season winter is here so the light is dim and cold
Here is a list of the cast back then and now
First appearance: “Winter Is Coming” (Season 1, Episode 1)