Certainly it's possible to be snobbish about it, but--for the most part--having unnatural materials in a natural planted tank tends to be jarring, especially when they're mass produced items that lack the level of detail of the actual living elements in the tank.
That said, it's possible to structure your tank such that a high quality non-natural item can be appropriate. One of my favorites is a very atmospheric tank that presents as a path thru a dark, spooky forest to a huge, resin "haunted house" style mansion. The level of artistry needed to blend the elements, though, takes a very good eye for design and detail.
And, yes, natural materials can offer benefits to the tank, especially when it comes to introducing natural wood pieces.