Actually, South America lost one spot due to the co-hosts in Europe. So Europe with 10 spots (Bulgaria, Italy and Poland with automatics). Venezuela is not strong enough for the tournament as the 3rd team in South America.
To me, it is questionable whether the 3rd African team (Cameroon/Algeria) or the 5th North American (Mexico) deserves a WCH spot more than Venezuela. Historically speaking, Venezuela has given the volleyball world talented players over the years and I think they should be at a WCH. An alternative would be to make an intercontinental qualifier, similar to FIFA's, and determine which continent gets the spot. But we are not talking about tournament-changing participants here, of course, so this is just an idea.
Regarding the European quotas, we should consider the generation change in some countries. Just like always, there will be teams that will look differently between 2 WCHs. One such team might be Finland. I doubt Kunnari and Esko will be super fit/still playing in 2018. Siltala may be, he will be 34 then. Another team like that could be Belgium. Depestele most probably won't be a vital part anymore and their game is currently entirely rotating around Sam Deroo. Bulgaria, Italy, and Poland are already there, Russia, Serbia, Germany, France should have no problems, whereas it would be very interesting to me which teams will get the remaining 3 spots. Belgium, Finland, and Slovenia look like decent candidates, but I see Turkey, the Netherlands, Estonia, providing that they all send their best available players to the qualifiers, closing in the gap. And I would love to see Slovenia's first-ever WCH participation, as well as the return of the Netherlands.