In a video with fineokay, Clumsy (one of the devs) made a comment on this sort of thing in regards to Mulan. He noted that an obvious buff to Mulan would be to have her 1 animation be much quicker. It would make her damage come out faster and she would be less likely to be interrupted. The problem is that sort of animation is done that way for both style and substance. It would look pretty comical if she moved a whole lot faster in that animation. So they look elsewhere in terms of buffs. There is also something to be said about players being hit by abilities being able to have a chance to react and respond. There is an argument to be made that some abilities taking longer to come out can be better for balance or just for making abilities look cooler and more fun.
Essentially, there are a great deal of gods that get better if their abilities are faster but there are several reasons they are hesitant to do it. There are balance and style implications. Hades 3 having a delay or Zhong 2 having a wind up allows for relic usage in response to those abilities as well as a chance to interrupt them with CC. I think those are kind of necessary drawbacks among others to tanky mages. In addition, I think you could argue those abilities look cooler as a slower animation. Maybe, Hades could be faster and it would be fine. I do think Zhong is an odd choice as he has been in and out of meta.