i dont think its got much to do with the tracks at all, the cars rely too much on downforce for cornering speed and dont have enough grip, get up behgind someone and you lose downforce, and then there is no way known you are gonig to get past anytime soon, if you a slower through the corners you are pretty much going to end up slower everywhere.
And yes ground effects are very dangerous when a car bounces off the ground, out of the tunnel at Monaco you could possibly flip over the part where the track decends quite quickly. Once te car gets too far to the ground, ground effects, have alomst no effect (thats why they call it ground effects
).
All in all, however its done, grip must be increased, and the draft created by the cars must be decreased before we see more passing, Silverstone is traditionally a palce where you see alot of passing, yet we saw Kimi get held up by cars that he could easily lap more than a second or so quicker than in clean air. That has to say something about F1. Safety is paramount, but i think they go just a bit too far with it, these cars are amazingly safe, and weve seen that they can hit concrete barriers at horrific sppeds, take alot of damage, and the driver is perfectly safe. You can never be too safe i guess, but you can definately get too bored.