I think pre patch the "bad defense" argument was starting to lose a bit of weight anyway, but now skydrop grants equal reward to the rest of the casts armor so... why is it so bad? The tracking isn't the best and it is quite slow, but it does its job blowing up gaps and such. On top of this he also still has some of the best offense himself, especially now he isn't risking getting launched with every ExRune/ExSkull.
You see, what most people don't understand is Summoner isn't just a zoner, he's a hybrid zoner and rushdown character. He has the best zoning along with some of the best mixups, with somewhat decent buttons.
You can fool yourself about the character being bad, but it might just be you. He has his bad MUs for sure, and I think Sorcerer is probably better than him now, but to say he's not very good is ridiculous. He doesn't really need to play the new meta, he still plays the old one and does it pretty well.