I'm not proban or anti-ban, would like to actually see aegislash in the meta for some time rather than outright quick ban it..
But can we not pretend that 50/50s had anything to do with its ban and won't be the reason for it to be banned? Its been the fucking worst argument since its x/y suspect that mostly everyone agreed was a bullshit reasoning anyway.
Aegislash was banned for centralizing the entire meta, checking almost everything in it and being too difficult to teambuild against without running an aegislash yourself. It was too unpredictable with its sub-toxic set, crumbler head smash set, and the fact it can pick or choose its walls either with a physical or special set. The 50/50 argument was never valid because there's plenty of 50/50 elements in the game, there was just nothing as godly at checking and countering the entire meta in one team slot. The only thing too difficult to predict about aegislash was the set it was running, checking it could instead just be a death sentence or an opportunity for it to setup. King's Shield had nothing to do with this, especially since not all physical attacks were contact moves anyway, Smeargle wasn't broken with it, and status/special moves were unaffected.
If 50/50s was a legitmate excuse; sucker punch, double switching, and the upcoming obstagoon would be immidiately restricted.
That being said, if it were to get banned, it'd be primarily for it being too damn good at walling and sweeping the entire meta, and like others have already mentioned, even old checks still can't handle it or lose to some of its sets. The only hope would be if the dynamaxed counters actually threatened aegislash, especially since it can't use dynamax well itself due to king's shield changing. A lot of dyna mons may manage the vital 2hko's, ohko's, or surviving the 3hko's inorder to beat aegislash.