What is the purpose of the colour-coding?
Counter question: Why does that bother you?
Would anything be different, if those items would have regular white tooltip, rather than green?

for the majority of items, you would expect them to be consistently useful ( in whatever they do )
Feel free to do your own counting:
https://baldursgate3.wiki.fextralife.com/Weaponshttps://baldursgate3.wiki.fextralife.com/Armorhttps://baldursgate3.wiki.fextralife.com/AccessoriesOr you can believe me that "majority" of items DO have consinstent usefullness.

and without illogical restrictions
This is just matter of point of view mostly ...
People keep complaining about "when you have 50% HP" items the most ...
I wouldnt say it translates to "you have to be half dead" ... after all, person with last 1HP is working in this game as just as healthy and capable of doing things as person having full HP, wich we are certainly not if we are single punch from beaing beaten to death ...
So you simply have to be wounded, wich is quite common condition in fantasy, in Dragon Age there is whole magic type based on spilled blood. O_o
Sure we can still ask who and why would create an Magic Armor that is powered by its own wearer blood ... but that is again just matter of poing of view.
Its creator could (just for example) see potential power in that spilled blood, and decided that if you are going to get hurt anyway, you could at least gain something of it, rather than just being harm without any use.
Or it could be failed experiment.
Or ongoing research, if that power of blood would actualy work.
Or it could ben sucesfull experiment, that didnt really catch with people.
I mean, this is the same story as with the tadpole over again ... there is countless (resp. as much as you can make) ways to explain things ...
You just need to open your mind a little, rather than just repeating "you would need to be bad, crazy, stupid, or all that combined to ... w/e" ... but ofcourse if that is the only explanation you are willing to accept ... well, its quite sad story i would say. :-/