It's very easy in retrospect for armchair critics to second guess the decisions of the race officials.  Especially with the benefit of hindsight and in the context of a serious incident having occurred.

To play devil's advocate for a moment, consider the following:
 1) The vast majority of drivers successfully navigated the track without incident.
 2) Waved yellow flags were displayed as per the regulations.  Drivers will have had to display a reduced speed through the effected sector.
 3) Despite some of the hysteria from some quarters about the race needing to be abandoned because it was too wet - none of the drivers (besides Vettel) had pitted to exchange their Intermediate Tyres for Extreme Wets.
 4) An increased risk exists whenever a recovery vehicle is operating.  Irrespective of weather conditions.

My personal opinion in this case is that there may be some questions to answer regarding the light levels, but fundamentally this was an extremely unfortunate accident rather than any form of negligence or recklessness.

(Remember when Eddie Irvine lambasted the race officials at Silverstone for stopping the race for 40min to repair barriers because, "I guarantee nobody will ever crash in that same spot!".   Sometimes lightning does strike the same place twice...)

Thoughts and prayers go out to Jules and his friends and family.