I know that I, for one, have almost never lost to Affinity before turn 4
You sir haven't played enough Modern then. I still lose to Affi or win with it on Turn 3. This involves one of the goldfish openings, nothing more. Not losing to Affi on T3 is like not losing to Humans on T4.
About Summer Bloom, it's not coming back also because some cards will be printed and help the deck become better anyway, at some point (that's all I hope for Amulet players, because this archetype is super interesting / rewarding to play). Cards that will be unbanned are the ones that haven't hurt Modern yet.
KCI is the first combo I've seen managing to win through 4 Meddling Mages.
You've not played / watched the format enough then. Med Mage wasn't played in the format before, that's why you never saw it beaten by another combo deck to begin with. Actually it was bad enough so it wasn't played, because combo decks could win through it anyway. I mean, Valakut, Vizier Company & Infect can be considered as combo decks and they win through Med Mage pretty easily.
Ban a deck (essentially) that isn't even doing well right now because it'll allow some aggressive printing
Storm is doing ok (Tier 2 isn't nothing). They banned Pod because it was getting stronger as cards were printed. Printings were already aggressive and Wizards didn't stop. They print whatever they judge good to print, they won't stop because it makes a Modern deck degenerate. They actually don't spot it when it happens, they don't even spot it when they break Standard in half with broken cards or combos.