Writers can do what they want, and they usually want to do something coherent. Synthesis is unscientific? "Unmasseffective"? Well it means that you can biologically explain reapers in Mass Effect 2! Yes, those creatures who are synthetics but have organic parts made with essence of organic life! "Unscientific"! Yes! "Unmasseffective"? Well, it means that mass effect 2 isn't "masseffective"? Mass Effect has never been hard science-fiction, deal with it.
Hm. I never argued that Mass Effect is hard science fiction. But Synthesis as it is described is not hard ,not soft ,it is anti science fiction.
Because if you try to analyze what is described in green ending it is an act of God,nothing less. Force that is capable of something like Synthesis can do anything.
Let me explain:
Synthesis is a beneficial integration of technology into numerous various living organisms ,simultaneously, all over the galaxy.
This involves: creating matter all over the galaxy,furthermore - matter that is created as functioning complex technological devices ,all over galaxy. Not only that,but creation of numerous drastically different variants of complex technological devices that need to interact with numerous various organic life forms with varying biochemistry,metabolism and what not,all over galaxy. Not only that,but interaction needs to be not only non-harmful, but beneficial.
This is achieved by plugging a device with mostly unknown function made by numerous different unknown designers into another device of mostly unknown function,made by different designers and a guy jumping in beam between the two.
It is unmasseffective in a sense that it introduces a God mode, no previously established rules of conduct of functioning of the ME and its powers even hints that something that is capable of such a feat exists in ME universe.
And Catalyst knows about Crucible and can have access to such a power that allows it to do ,well,anything - but ignores it and keeps sending Reapers every 50k years?????? This is a joke. Science fiction? There is more science fiction in folk tales. After non-sense like this anything can be written in ME lore.