Casinos with a Below average Safety Index usually have an unfavorable ratio of their number of visitors to relevant complaints submitted by players. It means that this casino has probably treated some players unfairly in the past.
We use the Struggling casino rating to identify smaller casinos that didn't manage to reach a large number of players or higher revenues even after being on the market for a relatively long period of time. It doesn't necessarily mean they are bad, but there might be issues if you want to withdraw big winnings.