Globally,
I do not believe that this accident is an indicator of UIO's safety. While the threshold for error is smaller than an airport with a longer runway, there is a clear and established procedure for landing at UIO... pilots who follow procedure do not experience a runway over run, at most they execute a go-around for another landing attempt.
As there has been no volcanic activity for some time here with the local volcano's I do not see how ash is a factor??!!