I think it all contributes really, the lack of mobile and the emergent gameplay that makes GvG unfun for anyone except the diehards. Most of the action takes place within an hour or two of recalc. Then because a guild can only get on the map at specific spots, guilds can lock those down and then control other parts of the map safely. Guilds are supposed to take losses on certain sectors, usually along rivers and mountains but that part of GvG is bugged, never worked right and likely will never be fixed so that screws up the balance. Doesn't matter how much you and your guild is built up if you keep running into a wall.
Then, unless you're a trusted guild member, you can't actively attack anywhere, you can only attack where guild leaders have a siege set up. If guild leaders are done for the day, you're SOL with nothing to do. GbG always has opportunities. Guild leaders can direct where they want players to go, and the attentive ones follow.
If anything, these changes to GbG are looking to be a net improvement because guilds had managed to learn how to wall off the competition there too. Now it's harder to pin guilds down and safely hold onto the middle. So far, my guild has increased GbG activity a little since the change.