My understanding is that the pilot flying was a highly experienced instructor transitioning from the Airbus A320 (with its different philosophies) to the 777. He was still flying with a training captain in the right hand seat, so probably less than half way through his line training.
Trainees (even experienced ones) make mistakes and he pretty thoroughly messed up the approach. The instructor in the right hand seat was on his first solo flight in that role in the aircraft. The instructors amongst us will know that there is a fine line in when to step in. He pointed out that they were high, but does not seem to have been providing height to distance information e.g x miles x feet above path. Where he comprehensively failed was in not calling for a go-around when the approach became obviously unstable.
Arguably this point was reached earlier. But by a thousand feet the aircraft was clearly not stabilised and latest then they should have gone around. Skybrary has interesting information about people pressing on with unstabilised approaches. In my opinion it continues to be one of the most frequent breaches of standard operating procedure.
The discussions about lack of manual flying skills and minimum speed protection are valid. But in this case an equally important conclusion is that even instructors do not seem to be go around enough minded. Particularly in line training we should be emphasising the need to for a missed approach if you are not stable.