I don’t think of “shoot” as just a toned-down “shit”. If “shit” expresses anger or rage, “shoot” expresses frustration and disappointment. Not the same.

I agree with you on “fudge” though, no one should be saying that unless taking about the dessert.

And to be clear, in this instance the artist just choose to use that word. Seems like the comic aims to be family friendly too, which is a valid reason to avoid the hard curse words. https://www.berkeleymews.com/comic/time-travel/