The seven deadly sins are all things that have a serious negative impact on you and your life if you give into them too much. They’re all very general habits/feelings/desires that most people feel/experience which can lead you to hurt yourself and/or others, and haste/impatience checks both those boxes.
And I suppose as “sins” they’re supposed to lead you to do “un-Christian” things, but impatience probably does that more than sloth, right? Like you’re much more likely to hurt yourself and/or others if you do things fast without thinking than you are by just sitting and doing nothing all day.
I guess all of the sins are also all some form of carelessness too which also applies to being hasty or impatient.
It’s a system of morality utterly based on magical thinking that begins with the dubious requirement of faith in the existence of an omnipotent creator, a laughable and absurd premise that to me at least, invalidates most of its subsequent conclusions.
I would hazard a guess that that most Christians would say that the sins are commandments from God, who purposely omitted the “sin of haste” for reasons that cannot be comprehended by man and that you should go read your bible. What I would recommend instead is to continue the ethical line of thinking about the harms of haste, look for real world examples, and seek out what other ethical thinkers have to say on the issue instead of trying to fit that exploration within the context of an arbitrary belief system that encourages you not to think at all.
I find Christian “ethics” to make much more sense when understood as an autocratic system of power rather than one that is trying to grapple with what it means to be “good”.