An earlier move to IOs and you could have dropped that axe years before shutdown. Though you'd have to go balls out for perma hasten and would probably be better off with a few seconds downtime and better defense.
IOs provided better benefits than Hasten itself in many if not most cases. First, there was a lot of global recharge floating around in the IOs from the LotGs to the purple sets to the cheap recharge in many other sets. Second, IO set slotting allowed people to slot a lot more recharge into click powers that could benefit from recharge without significant penalty (or often without any penalty at all). Third, Hasten itself contained costs that players often ignored but still existed, and IOs could eliminate. Consider that if you got Hasten to be just perfectly perma, you'd be cycling it about every 120 seconds. Actually, you'd have to cycle it slightly faster than that to prevent a gap, but let's say 120 seconds. Hasten had a 0.73 activation cost, which was actually closer to 0.93 seconds with Arcanatime tailgating. That means 0.93 seconds out of every 120 seconds you can't activate attacks. That's essentially a 0.78% damage debuff of sorts when you can't attack (or for that matter, can't use other beneficial clicks). Hasten also had an endurance cost, except it happened on expiration rather than activation. Still, it burned 15 end every 120 seconds (when perma) which could not be slotted away (I'm pretty sure conserve power didn't do anything to that cost either). That's 0.125 eps. That's not high, but its not nothing either: a reaasonably slotted SR toggle would cost about 0.195. So (perma) Hasten burns endurance almost like a toggle. In the world of inventions that SR toggle would cost less while Hasten continued to cost the same amount.
Global recharge bonuses could easily get you into the +25%ish range, and extra slotting could get +40-50%ish more recharge than pre-IO days, giving attacks as much recharge as perma-hasten used to with no activation penalty, no extra endurance cost, and no gapping under recharge debuffs (if you're hit with a recharge debuff that could increase the recharge time of hasten to the point where it is no longer perma, and then you lose the benefits of the buff during the downtime: that can't happen with global or slotted recharge bonuses).
On top of that, you can still take Hasten. But IOs created paths to equal or higher net recharge with less costs than Hasten. And we're not even talking about lunatics like me that built builds approaching 200% recharge - like having three copies of hasten stacked.
Perma-Hasten vanishes in I6. IOs start showing up in I9. So there's only a seven month gap in the eight+ year history of the game where the lack of perma-Hasten was really much of a thing. And once I9 arrived, I didn't miss (easy) perma-Hasten at all. I think I said once that if I knew then what we were going to get in I9 and beyond, I would have asked for ED in Issue 1.