Two things to consider, IMO.
Firstly, the minnow nations are generally better this time than in 2003, IMO. Most of the stronger minnow nations (excluding Canada and Bermuda, in other words) have some quality home-bred players and you can see a general improvement in professionalism and standards when compared to previous outings. The likes of Ireland, Scotland and the Netherlands aren't really much worse than Zimbabwe, if at all, and I don't think they ruin the tournament with their presence, and there's the realistic prospect of competitive games. Guys like RtD and Morgan deserve a chance to shine on a big stage, too. Canada and Bermuda clearly aren't good enough, but they'll only play three games each and then they'll be gone.
The other issue, and the key one for me, is that it's the World Cup. I don't see the problem with even woefully substandard teams appearing in one tournament on four year intervals. I think it's problematic to hand out ODI status to teams who simply aren't competitive against other minnows, and guys like Porterfield with huge averages and no experience against quality opposition are a bit much. Still, the World Cup should represent a wide cross-section of cricket nations, and I think 16 teams is a nice balance. We'll still end up with the best teams competing at the end, but the WC wouldn't be the same without some minnows involved, much like in the Rugby WC.
Over time I think we'll see more competitive performances anyway. Bangladesh and Kenya are clearly far better today than 10 years ago and continue to produce useful players, and I'm sure other nations will follow suit.