There is a degree of experimentation that you can do on the international stage. You can play around with the backrow for balance. As Peat said, Wood at 8 wouldn't nearly be as bad if there was a ball carrying 6 and 7 alongside him. But the reason this works is that Wood is essentially a blindside with an 8 on his back. He doesn't have to adapt his game. The experiment is effectively over whether he can control the ball at the base of the scrum.
However, when he replaces the England 8, there's a level of carrying that goes missing that isn't filled. This is the type of experiment that is predictably going to go wrong. It assumes that Wood will suddenly improve his carrying game to be worthy of an international 8. It is never, ever going to happen in the brief time Lancaster has Wood for international periods. It's the type of experiment that needs to happen at club.
Brown/Foden on the wing didn't work, but I don't necessarily mind that experiment, as they have the skills. Tuilagi, on the other hand...
So yeah, experimentation isn't necessarily bad. But expecting a player to come up with skills that they don't have in order to adapt to a new position isn't quite so good.