You're right about saturation attacks eventually overcoming every air defense. But the ~200 missiles from Iran would have been manageable for Iron Dome, if they were the kind of missile Iron Dome was built for – slow, short range rockets and mortars.

These were much faster, at least some of them maneuvered during flight and a lot of them had a terminal booster, so they were much faster.

Israel has systems for that, namely Arrow 2/3 (the latter even intercepts exoatmospheric and it looks fucking dope) and David's Sling. But they are definitely not made for the sort of massed attack we saw. They're more like a Patriot system.