Tasmiyyah On Fish
It has nothing to do with blood in my understanding, rather its the nature of the act (the act of taking of a life) i.e. there’s this act of taking of a life, the severity and realization of which can only be experienced while slaughtering ruminants and birds, therefore such acts can only be executed with izn of Allah. In case of a fish, there’s no such taking of a life in terms of the nature of act being done on them, therefore, the compulsion of taking Allah’s name on them has been relaxed.
If we are convinced that the requirements of mentioning God’s name is only on certain land animals, a more plausible reason seems to be that it’s a requirement to replace the prevalent practice of mentioning names of false gods or saints while slaughtering animals in the pagan culture. It’s got nothing to do with “ways of killing”. Since the pagans were not slaughtering fish so Allah did not require us to mention His name. This would also mean that eating McDo is fine as they don’t slaughter chickens in the name of false gods.