Players right now just need to instaclick(that is click super fast to block approaching melee) to generate walls. This causes melee units to be blocked BEFORE the attacker even realizes their block and pathfinding to act up before a wall is in progress.
Alas this is really a unfair bonus for the defender.
Initial wall segments can be walked over but players only need to complete 5% to effectively block a player. Can game developers change this to requiring walls to be completed befor ethey block the army and take longer for walls to complete.
When de first came out they already changed the blank wall segments which used to block players but the current version of walls is still favouring projectile armies over melee. Lots of abuse with walls among top players.