The thing about these missile defence systems is that, regardless of how advanced a system is, it can always be overcome by sheer volume of fire.
A common tactic is to saturate the sky with cheaper dummy missiles/drones that don’t even have warheads, just to deplete missile defence stockpiles and protect the real missiles/drones from being intercepted.
This is happening a lot in Ukraine too.
TLDR; You’re right to believe Iron Dome isn’t invincible because there’s no such thing as an invincible missile defence system.
The thing about these missile defence systems is that, regardless of how advanced a system is, it can always be overcome by sheer volume of fire.
A common tactic is to saturate the sky with cheaper dummy missiles/drones that don’t even have warheads, just to deplete missile defence stockpiles and protect the real missiles/drones from being intercepted.
This is happening a lot in Ukraine too.
TLDR; You’re right to believe Iron Dome isn’t invincible because there’s no such thing as an invincible missile defence system.