I'm a bit of a F1 buff, and was sad enough to have been watching this from 5:30am today. Three things went wrong here and none of them were to do with how safe the cars are.
Firstly the use of JCBs to remove damaged cars while the race track is live has been complained about for years. Secondly Charlie Whiting the race director messed up, people were calling for a safety car before sutil went off. When he went off it went to double yellows and not a safety car, the safety car came out after Jules' accident. Thirdly, the FIA twice asked if the race could be held earlier, and both times the race organisers refused, something went badly wrong if the people responsible for safety can't make that call.
1: This I could possibly agree with, although requiring a safety car every time a car needs to be wheeled off seems excessive to me.
2: What "people"? The majority of the field were still happily driving around on intermediates. There was zero indication prior to the incident that the track was unsafe.
3: Hindsight is a brilliant thing. There was heavy rain forecast throughout the day. If they had started earlier, the heavy rain that delayed the start would have happened during the race.
This was a very unfortunate accident, as happens in motorsport sometimes. But I don't see any reasonable way to blame the organizers.