From your link
'Carrie Fisher's fame as an actress rested on just one role, but it was a role in one of the best known and most successful film franchises in cinema history"
And this is so true
The 2 main reasons for this is;
1. She was manic depressive (old name for it) aka bi-polar. It made concentrating on doing the job very hard for her. This lead her to take illegal drugs; mainly cocaine. She would do cocaine to bring her up and booze to bring her down.
2. She got type-cast as Princess Leia. This is a curse for actors who perform an iconic role, especially at an early age/beginning of their career.